Month: November 2013

1) PDO...PDO...PDO

You know, PDO is a funny thing: dismissed and ignored in equal measure, but it works just as it says it works (Grayson on (PDO) regression). PDO regresses toward the mean although some (good) teams sustain higher PDO's throughout the season, which may be due to the score effects boost that a team receives once it's one, two or three goals to the good.  

Defeats for Man City and Tottenham may have been the two biggest shocks of the week. Both of the defeated teams faced opponents with crazy low PDO's at the time of fixture. Newcastle saw their PDO rise by 9 percentage points. Sunderland saw their PDO rise by 5 percentage points. #Regression.

2) Man City

I'm not bitter about Man City's failure to beat Sunderland. FUCK! F%$&*! It's a red card! In all seriousness, City boast a fine squad that should be more than capable of absorbing injury to players, no matter how key those players may be. Man City failed to create too many clear chances despite the imbalance in the shots and territory count. I have passed through most of the stages of grief in regards to City's away form and I'm now at total acceptance. We've have had problems with away form for the past 3 seasons, so it's probably not personnel or coaching strategy, which have both improved, so what is City's problem away from home? If you know what is ailing City away from the fortress let me know!

3) Man United Title Contenders?

Alan Hansen seems to think so (LINK): AH: Moyes needed desperately to make a big statement after falling short against Manchester City and Liverpool already this season and to beat the league leaders, who have been flying, just shows that talk of United’s supposed demise is totally unfair. Now, Man United's win was mighty important. It was a vital 3 points against an Arsenal team who, although riding some percentages during their first 10 games, are a strong team. United managed to win the game by scoring early and then forsaking any attacking intent in order to prevent Arsenal from creating any scoring opportunities. Once into the lead Man United were out-shot 3-10 for the ~69 minutes of the game. United's shell worked but it was a shell without any counter attacking threat. An ultra defensive strategy, like the one United employed against Arsenal, needs to be tight defensively but it also has to have a counter attacking element to it. Getting an early goal and then sitting back and barely launching meaningful attacks for the remainder of the game probably isn't a strategy you want to employ too often against good teams AH: It will also have erased some of the doubts that have been hanging around Moyes since the start of the season. Nope, I'm not buying that. United's win was an important one but did it really erase doubts about Moyes? Maybe it did for Hansen, but not for me. United's underlying shots and shots on target numbers are really not that impressive, in fact they are barely scraping above league average. Moyes is failing to reproduce Ferguson's set-piece magic or the ability to secure 'from behind' wins. Gone is the efficiency in getting shots on target at a high rate and preventing the opposition from doing the same. Moyes needs time to figure out his players, needs time to adapt to what his squad can and can't do. Will Moyes get there eventually? Maybe. But I don't think he has the system in place to win the league nor the depth of outstanding personnel to overcome those systemic inefficiencies.

4) Player Of the Week

Take a bow Tim Krul. A wall, a one man barrier, superman. As far as I am aware, 14 saves is a record in the OPTA era. So yeah, unlucky Spurs fans.    

5) Southampton & The Fixture List

Southampton are flying! 3rd in the table with 22 points. 15 goals for, 5 goals against and simple math says they are on course for a mind-bending 76 points. Southampton are out-shooting teams and are as defensively sound a team as you are likely to find. But, my has the fixture list been on the easy side so far: Sunderland, West Ham, Palace, Swansea, Fulham and Hull have been Southampton's home opponents. An easier home list you will not find. Away from home Southampton have faced West Brom, Norwich, Liverpool, United and Stoke. Admittedly more difficult but  Southampton's fixture list has been mighty easy so far: Numbers taken at the time of fixture. Southampton's opponents have been poor shots team, unlucky teams (PDO) and sub-par territory teams (Final 1/3rd and possession%). Maybe this writer is slightly harsh on Southampton. After all, you can only beat what is in front of you! Upcoming fixtures:

Southampton's upcoming PL fixtures: Arsenal (a) Chelsea (a) Villa (h) City (h) Newc (a) Spurs (h) Cardiff (a) Everton (a) Chelsea (h). #fuck — Ben Pugsley (@benjaminpugsley) November 11, 2013

  Let's reserve judgement on who Southampton are until the 19 game.  

6) Open Play Shots

This is a pretty simple table: remove shots f/a from set-piece situations and this is what a simple plus/minus table looks like. Tottenham, City and Chelsea round out the top 3. Man United are just +16 in 11 PL games which is, well, not great and it points to those fundamentals I talked about earlier. Swansea are the biggest surprise for me: -11 at set-pieces, Swansea are +34 in open play which is good for 4th in the league. Some pretty nice numbers there for a team on a budget. Fulham and Cardiff are adrift. The bottom 5 are the usual suspects.

7) Injury And European Football

As stated in the previous point, Swansea are a pretty nice team by the open play numbers. So it's would be a shame to watch as the team struggled with the log-jam of games in November and December. Swansea, and other European teams, face 10 games (or more) in 36 days once the PL resumes on November the 23rd, and this jam is sure to take it's toll in terms of injuries and player fatigue. Injury data from the 2012/13 season. Swansea's small squad, the European games and the Thursday-Sunday fixture list may take it's toll on team selection and, ultimately, Swansea's ability to claim points. European teams suffered last year in terms of Injuries and December was the real hot spot. Swansea seem to be a prime candidate to suffer injury and a possible drop off in points. Ditto Arsenal?

8) Game State & Shots

More graphs! Here is the PL after 11 games and the percentage of shots that occurred at each game state. A couple of things stand out. First is that the percentage of shots taken at close game state looks slightly high at84.71% which leads me to think that we've seen quite a few games this season that have been closer (within 1 goal) than last season. If we have seen closer games this term that may be one reason for the Premier league's low scoring% this term which sits at 28% (it's usually around 32%). The other key piece of information on this table is the imbalance of shots at minus 1 compared to plus 1. 19.93% of all shots taken in the PL this year have come from the team down a goal, with just 17.67% of shots taken by the team up by a goal. This is what we call the shell: teams that are up by a goal tend focus on defensive shape and holding onto the lead. teams trailing by a goal tend to shoot more frequently and enjoy a territory advantage. Why would the leading team sit back on a one goal lead when they could easily continue doing the good things that enabled them to get into the lead in the first place? The leading team probably feels that preventing the opposition from scoring a goal is far more valuable than searching for a second goal of their own. The defensive shell.

9) Referees

Oh, it was a bad week for the men in black/yellow/salmon/green. Terrible late penalty decisions were given against Swansea and West Brom who both lost two points a piece.  My astonishment for Ramires' dive was surpassed only by my horror at the fact the referee awarded a penalty for the supposed foul on the Brazilian. It was a terrible decision and heartbreaking for Steve Clarke and his men. The following day the referee in the Swansea v Stoke game gave a 90th minute penalty against the home side for a handball in the box. I have a few issues with his decision: 1) The referee was un-sighted. 2) It wasn't a handball. 3) No player (that I recall) appealed for a handball. So, no handball, no appeal and the referee couldn't see the incident. yet, the referee gave the penalty. Referee's have a difficult job, it's stressful and incorrect decisions will be made, but my Lord we saw two horrendous incidents this week. I'm obviously impartial when talking of these incidents. It's not like I lost money on Man City or Swansea failing to win! *I lost money on both games! Oh, and don't forget this. No card for what can only be described as a leg breaker.

10) Goal Of The Week

Yeah. As for the PL, check out Stephen Ireland capping off a great Stoke team move.

Arsenal’s mid August crisis seems so far away at this stage.  At that time they had just lost their opening game of the new season at home to Aston Villa and Gunners’ fans were disappointed at Wenger’s typical Scrooge like dealings in the transfer market.

Then Mesut Ozil signed on the dotted line and all has gone swimmingly for Arsenal since then.

Following their comprehensive 2-0 win over Liverpool on Saturday evening, Arsenal now sits 5 points clear of the chasers at the top of the Premier League.  Their critics would say that they have faced an easy set of fixtures so far; and they would have a valid point.  The current average league position of the teams that Arsenal has faced has been 13^th, which compares with the average position of 10^th for Chelsea’s opponents. Still, Arsenal can only beat the opponents they face on each match day, and in they have done that 8 times since their surprise upset to Aston Villa.  Their only less than perfect league result has been away to West Brom at the start of last month.

I’m keen to get a look at what the shots in Arsenal’s games can tell us about how they have performed and whether their league leading position after 10 games is justified.

Arsenal’s Defence

Although it’s been Arsenal’s attacking talent such as Ozil, Giroud, Cazorla and Ramsey that has received most of the plaudits I’ve been seriously impressed by the Arsenal defensive performance.

Here is the Shot Chart for the shots that Arsenal has conceded in the opening 10 games of the 2013/14 Premier League season.  And for those unfamiliar with these Shot Charts I am also showing the template that defines the boundary between the four zones that I use:

Arsenal has conceded 9 goals this season, but the two penalties scored by Sunderland and Aston Villa are not included in the above chart.

The concession of 125 shots is not elite; in fact the average EPL team has conceded 129 shots.  However, what Arsenal has done superbly is limit the amount of dangerous shots that they give up.  Their concession of just 31 shots (3 per game) from the Prime Zone is the best in the league; Tottenham, Man City and Everton are next best in this measure with 35 shots.

ExpG

The result of preventing shots from good locations is that the average goal probability per shot allowed by Arsenal (at less than 7%) is the lowest in the Premier League.  I posted the following image in this look (link) at Roma, but it’s worth publishing here even if the figures do not take the latest round of games into account.

Out of the 98 teams in the Big 5 leagues, only one team, Roma, forced teams to take shots where their average goal probability per shot was less than that allowed by Arsenal.  That metric must bring tremendous satisfaction to the team and their coaching staff.

I am measuring the average goal probability by using the ExpG measure created by Constantinos Chappas and me.  Some outline details about ExpG can be found in this article, but as we use this metric for betting purposes we’d prefer not to reveal the full details of the calculation method.  Incidentally an approach similar to this ExpG model seems to be used by Prozone and Joey Barton recently published some of Prozone’s stats on QPR.

At least we seem to be in good company…….

As well as owning the best average ExpG value allowed per shot, Arsenal have the lowest aggregate ExpG value conceded in the league.  This suggess that the Gunners are defensively sound and means that, on the whole, Arsenal’s low goals conceded total of 7 (excluding those 2 penalties) is deserved.  Although there are four teams that have conceded fewer league goals than Arsenal I would contend that the Goals Against column for those teams (Chelsea, Spurs, West Ham and Southampton) are much better than the shots they have given up would suggest.

Southampton

The most extreme example of this is Southampton where they have conceded just 4 league goals.  Using the ExpG value for every shot conceded I ran a simulation which replicated the 97 shots that Southampton has faced this season 10,000 times.  In only 2.03% of these simulations did Southampton concede 4 goals or less.

Perhaps Southampton are doing something different where the probability of a team scoring against them is less than the average team in our data set but I don’t think so.  This incredibly low probability suggests that the Southampton goals conceded number is going to see some regression in the near future as the variance that they are currently getting the benefit of will turn on the Saints.

Who knows?  Perhaps Asmir Begovic’s goal for Stoke against the Saints on Saturday is an indicator of the “bad luck” that may be ahead of Southampton.

Arsenal in recent games

What’s even more impressive about Arsenal’s defensive performance is that they have improved as the season has gone on.  In 3 of their opening 4 games Arsenal conceded more than 1.00 ExpG (that is our estimation of the number of goals that a team should score given their shots); and their opposition in these games included Aston Villa, Fulham and Sunderland – none of which could be categorised as strong opposition.

However, in each of their last 6 games their ExpG against has been less than 1.00 and they conceded just 4 goals in those 6 games, so it’s not by luck that opposition teams are feeling frustrated after facing Arsenal.

I have seen Mathieu Flamini singled out for praise upon his return to Arsenal’s defensive system, and our ExpG numbers would corroborate that fact.  It’s probably no coincidence that he missed Arsenal’s opening two games of the season (when Arsenal shipped 2 of their 3 highest defensive ExpG figures).  The introduction of the French man has corresponded with a tangible decrease in the chances that Arsenal have given up.  

Arsenal Going Forward

Arsenal’s 142 shots represent the fourth highest volume of shots amongst teams.  Liverpool has also had 142 shots, and that pair trail behind Trigger Happy Tottenham, Chelsea and Man City in terms of efforts on goal.

Arsenal is very careful with their shooting locations, with no shots so far from the Very Poor Locations zone and 44% of their shots come from the Prime Zone which is well above the league average of 37%.

That Prime Zone figure of 44% is bettered by just Man City, West Brom and West Ham; with all of those teams have more headers than Arsenal.

The significance of this is that a team that has headers making up a larger proportion of their total chances would expect to see those chances originating from closer to goal than shots.  The trade off here though is that headers are converted at lower rates than kicked shots from all spots on the pitch.

All of the above means that Arsenal, although very good, from an attacking point of view have not been exceptional when analysed through the lens of our objective ExpG measure.

Man City, Chelsea and Liverpool (by virtue of their excellent average shot probability) all post aggregate ExpG values in excess of Arsenal’s number.

For the record, we have Man City with an ExpG of 8 higher than Arsenal, and Chelsea and Liverpool both at 3 goals higher than Arsenal at this stage of the season.

It’ll not surprise anyone when I therefore contend that although Arsenal has been a joy to watch this season they have over-performed in scoring 21 goals from their 142 shots. I processed Arsenal’s 142 shots through my simulator and on just over 10% (10.13%) of the simulations did Arsenal score at least 21 goals from the shots they took on. So, the over achievement of Arsenal in front of goals is not quite as significant as Southampton’s in stopping the goals being scored but, for my money Arsenal’s current goal tally of 21 goals (excluding the Giroud penalty) is somewhat inflated given the shots they have taken.

Aaron Ramsey

One of the stars of the season so far has been Aaron Ramsey with his 6 Premier League goals.  The Welsh midfielder has significantly upped his performances this season, probably due in no small part to the increased confidence that finding the net brings with it.

However, Ramsey is a perfect encapsulation of how Arsenal has scored more goals than the shots they have taken would suggest.

Using the same simulation methodology as above I have ascertained that Ramsey would score 6 goals less than 1% (0.85%) of the time based on the shots he has taken this season.

Even without access to advanced metrics, we know that shots are scored at a rate of approximately 10%.  Ramsey’s average shot location is certainly no better than would be expected for the league as a whole.  This simple logic would dictate that Ramsey would have been expected to have scored 2.30 goals from his 23 shots, not 6.

I want to be clear that our ExpG model uses much more complex inputs than laid out in the preceding paragraph, but even those simple numbers can give a sense of Ramsey’s over achievement in terms of putting the ball in the net.

I’m including a plot of all Ramsey’s shots this season and I spent some time trying to think of whose shots I could compare against.  I eventually settled on comparing the shots that Ramsey has taken this season with those taken by the same player last season.

The current season shots are the green dots, with the red and yellow checked dots representing the shots taken by Ramsey last season.

I think it’s fair to say that the general shapes of the shot locations are roughly similar from last season to this.  It is therefore surprising to see that last season Ramsey only scored 1 goal from his 46 shots, yet this season he’s shooting the lights out with 6 goals from half as many shots as last season.  You’d barely believe that these shots were struck by the same player.

I’d suggest that the true Aaron Ramsey conversion rate is somewhere between the two extremes, but the above image is a powerful reminder as to how much variance can exist when analysing individual players’ shots due to the relatively low numbers taken per season.

Interestingly, Ramsey’s variance of 6 actual goals against his 2 ExpG actually explains the majority of Arsenal’s attacking over achievement.

Summary

When we combine our attacking and defensive ExpG values for the entire Premier League, we rank Arsenal in third place overall, behind Man City and Chelsea.

Defensively they have been superb ensuring that teams shoot from unattractive locations, but the fact that Arsenal currently tops the league is partly due to variance in my opinion, and unless the Gunners create more and / or better attacking chances I would expect them to come back towards the chasing pack.

As a result of Arsenal’s relatively gentle start to the season in terms of opposition faced, it is inevitable that their strength of opposition will toughen up between now and Christmas.  In the event that goals start to dry up for the North London club the media will probably latch on to the fact that Arsenal have found it tougher as they face better opposition. In my opinion, this will be misguided as Arsenal is due a goal scoring regression regardless of who they face in their upcoming fixtures.

PDO

Another way of visualising the “luck” element that Arsenal has benefitted from this season is through PDO.  PDO is a concept that has been taken from ice hockey and it is supposed to measure luck by adding together the % of shots that a team scores and the % of opposition shots that they save. In summary, the league average is 100, and a number greater than 100 would suggest that a team has been lucky.

Our own Ben Pugsley has been keeping a record of PDO (amongst a host of other stats) over on his Bitter and Blue blog, and he has updated the stats for GW10.  His stats tables can be found here.

Arsenal tops the PDO table after 10 weeks.  Now I’m not totally convinced by the merits of PDO as it has at its core a belief that all shots for and against are equal, and I have shown that Arsenal allow poorer quality shots than anyone else in the league.

Still, even with that proviso I think it is useful to show that there is a measure other than our ExpG that shows that as good as Arsenal have been they are perhaps in a little bit of a false position.

I think it’s important for Arsenal fans to recognise this; they can certainly bask in the warm glow of being league leaders but be aware that the shooting performances suggest that there are currently one or two better teams in the Premier League than the Gunners.