I was kind of curious as to how Tottenham’s share of the shots (TSR & SoTR) and share of the goals (Goal%) looked during the 2013/14 season pre and post AVB. Having completed that task and seen the results (which I will get to), I thought I’d go back and look at Tottenham’s previous 2 seasons for which I have data.

Just to make certain that everyone understands the stats that I will be talking about, here is a quick reminder:

TSR – share of the shots taken.

SoTR – share of the shots on target taken.

Goal% – share of the goals scored.

PDO – scoring% (goals f/shots on target for) + save% (100-goals a/shots on target a).

Good. I’ll start with Tottenham’s 2011/12 Premier League season to warm things up for the main event.

2011/12 – Harry Redknapp

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So Tottenham, under Redknapp’s management, had plenty talent – Modric & Bale – and posted a 61% share of the shots (TSR) and a 59% share of the shots on target (SoTR). Fine numbers.

Tottenham’s share of the goals finished at 63% which is more or less in line with season-end TSR. But as you can see from the graph above Tottenham’s share of the goals (goal%) was a lot higher than TSR for the first 27 or 28 games of the season. The reason for this? PDO. Tottenham’s PDO was ~1100 for the first 28 or games or so and this enabled Tottenham to post a higher share of the goals than their TSR would’ve suggested.

Still following? I hope so. In short: if a team posts a goal% way higher than their shots or shots on target share then it may well be safe to conclude that a big part of that overperformance is due to high shooting percentage and/or a high save%. Conversely, a goal% that is lower than a teams share of the shots or shots on target may well have been suffering from a low scoring% and/or a low save%.

Just theories for now, but we understand that scoring and save percentages, given time, regress back toward the mean somewhat.

Redknapp’s final season saw early overperformance driven by a high PDO, which then regressed. Tottenham, more or less, were a pretty good team who finished with a goal% in line with their TSR%. 

2012/13 – AVB

Now to AVB

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AVB improved upon Redknapp’s strong shots numbers and finished the season as a 65% TSR and Shots on Target Ratio team. Both of those shots ratio numbers are superb.

The problem? scoring% and save% (PDO) were subpar (below 1000) for all but three games of the entire season. This caused Tottenham’s goal% to fall to 58%.

Villa-Boas was able to coach this Tottenham to outshoot the opposition and dominate the play but what he couldn’t coach may have been something out of his control and that was the rate that Tottenham converted their chances (scoring%) and prevented the opposition from converting their chances (save).

Now, Tottenham’s low PDO – and thus goal% – may have been influenced by poor shots locations, or personnel issues, or tactical issues or whatever. The problems with PDO will likely also have been caused by what is loosely termed as ‘bad luck’. It is almost impossible to tease out the exact cause of Tottenham’s woes – there’s likely some systems issues and there’s likely some ‘bad luck’.

Shit happens, but that shit really handicapped a Tottenham team who had shown excellent ability to control games and outshoot the opposition.

*****

Now to the good stuff.

2013/14 – AVB (16 Games)

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These are Villas-Boas’s final games as Tottenham manager and final games before he officially became damaged goods, and even “a manager with a defective tactical system”.

Tottenham’s TSR was ~62% at the time of his sacking and the SoTR was ~58%. Both of those numbers, while good, are still down on the previous season (Bale’s exit?).

Still, those numbers should be good for a top 4 battle, the problems for Villa-Boas, once again, were caused by Tottenham’s inability to convert chances (scoring%) and preventing the opposition from converting their chances (save%).  A series of hammerings wrecked Tottenham’s PDO and thus impacted their Goal%.

This time it wasn’t so easy to use ‘bad luck’ as the cause for the low PDO and goal%.  Villas-Boas’ systems (high line and inability to penetrate in attack) were spotted early by football media and used as a facile excuse for Tottenham’s failings. The reality was less clear.

Yes, Tottenham played a high line which was, on occasion, completely wrecked, but it also worked in many games that Villa-Boas deployed it. As for the lack of penetration in attack, meh. Soldado wasn’t helping, neither was Townsend or many of the other baffling personnel decisions, nor was a league high number of minutes spent in a tied position.

Villa-Boas’ tenure saw Tottenham control games and post excellent shots numbers but either ‘bad luck’ or ‘bad systems’ or a combination of those and many other factors saw Tottenham’s Goal% significantly lower than their TSR and SoTR numbers would’ve suggested. People call PDO a coach killer, and for good reason.

2013/14 – Sherwood

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Of all the candidates dotted throughout europe, Tim Sherwood was deemed to be best qualified, either through talent or familiarity, to coach Tottenham Hotspur. And who am I to question Sherwood’s appointment, after all 23 points in 11 games is mighty good form!

Sherwood restored Adebayor to the lineup and was rewarded with timely goals. The systems were tweaked slightly and Tottenham piled up the points. All is good, huh? Well, not really.

Sherwood has Tottenham posting the lowest TSR (~51%) and SoTR (~48%) numbers of any Tottenham manager in the last three years – significantly lower than Redknapp and lower still than AVB’s teams. Score effects may play a part in the decline of those shots numbers, but it does not by any stretch of the imagination explain all of the decline. Nor has Sherwood faced particlarly tough competition which could explain the decline. Sherwood has simply taken AVB’s team, tweaked personnel and tactics and turned it from a 62% TSR/58% SoTR shots team into 51%/48% team.

A shots drop that dramatic is rare indeed and it’d be mighty interesting to watch Tottenham’s zone entries to see just why they are no longer generating the same number of shots.

(*Villa-Boas team were taking 17.3 shots per game and conceding 10.8 per game. Sherwood’s team are taking 12.5 shots per game and conceding 12 shots per game.)

Still, what does the average fan care for drops in shots rate, or drops in TSR or SoTR? Tottenham are winning, Adebayor is scoring at a fast and easy rate, the players are “confident and happy” again, the points are piling up. The problem is, all the points and and goals are built not upon an ability to out-chance the opposition and dominate the shots count but upon an outrageous PDO of 122.75.

To my knowledge I have never seen a PDO that high over an 11 game span and that PDO is causing Tottenham’s Goal% to sit way above (64%) the normal levels that Tottenham’s shots share (TSR & SoTR) suggest it should be. Tottenham’s form under Sherwood is being powered by a statistic which is commonly referred to as ‘luck’ and that statistic tends to regress pretty heavily back toward the mean of 100.00.

I am aware there may be Tottenham fans who will argue  that this PDO (scoring% + save%) is powered not by ‘luck’ or unexplained variables but by systems and personnel and skill and the speed of attacks (which can be a part of PDO.) Maybe Tottenham fans are right to suggest skill and sytems are powering this hot streak of form, but to suggest this they would be indicating that Sherwood is a tactical genius, or a master psychologist, or that Adebayor has morphed into a world class striker, or that Tottenham’s attacking speed has dramatically improved, or that the defensive and attacking systems are the leagues best and that is why that PDO stat-thingy is the best in the the league over the last 11 games.

And maybe if all those things are real and those things and are really driving that PDO number, then maybe they are sustainable and Tottenham can continue to take a 64% share of the goals while only taking a 51% share of the shots, and maybe’s and if’s into infinity!

If you are a Tottenham fan who believes that this form, with those average shots numbers, is sustainable then you are suggesting that maybe Sherwood is a tactical genius, maybe he does make the players happier, maybe Adebayor is now a world class striker.

Thing is, if you do believe Tottenham’s form is sustainable without dramatic improvement in an ability to outshoot the opposition then you are betting on an awful lot of maybe’s continuing from now until the rest of the season and beyond.

Sherwood may be a genius, Adebayor may now be a world class striker, I don’t know. But the way PDO regresses and a little history close to home (graph 1 – Redknapp) tells us that PDO’s that high and goal%‘s that far seperated from TSR%’s don’t tend to continue forever.

To me good coaches produce teams that outshoot the opposition in terms of shots and shots on target in most game situations while creating the very best quality chances they can and preventing the opposition from creating good chances.

Andre Villas-Boas had the shot dominance part down, but was handicapped by the scoring% and save% elements of performance.

Sherwood is producing teams that are completely average by the shots dominance count but have bananas high – like Barcelona high – scoring percentages and strong save percentages.

Long term, which manager type is the better option?

*****
Bonus

20011-2014 – TSR, SOTR & Goal%

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Rolling

Sherwood’s full 11-game reign is the very last data point (far right). Worst SoTR, 2nd worst TSR, Highest PDO, abnormally high Goal%.

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  • Vladimir

    Excellent post. I see after the game versus Norwich some pundits started to blame Europa League, long trip to Ukraine etc…

  • Miki

    Does this system take into calculation the quality of shots taken? AVB, for instance, was quite keen for his team to shoot from distance. If I understand the maths behind this correctly, that would bring down the scoring% and thus PDO, right?

    • gjames

      I’d say the big upswing in PDO post AVB was entirely predictable and I’m past seeing the merits in the “AVB built a great but unlucky side” argument. It was a really good example of -why- PDO might regress to the mean during a season, as coaches who consistently get poor PDO are eventually and rightfully sacked and replaced*. Of course, an alternative is for the existing coach to spot the flaws causing low PDO and make the necessary adjustments, and while all the world could see the problems with AVB’s system (and teams grew to exploit them), AVB was far too stubborn to ever do that.

      *I haven’t looked it up, but I’d guess that the most stable teams in terms of PDO over the course of a single season are the ones that don’t sack their coaches.

  • Errorr

    I’m still questionable about AVB and his system but I still believe he was very unlucky at least some of the time. I always think back to the Newcastle game where Krul turned into the worlds best goalkeeper for 90mins.