This Saturday Rangers host Celtic in the second Old Firm derby of the season. Steven Gerrard's side are within touching distance of the champions. A Rangers win would put the teams level on forty-two points at the top of the Scottish Premiership, igniting a title race as we enter 2019. However, Brendan Rodgers' team does have a game in hand and a superior goal difference so a victory for Celtic would set up a significant lead. The early kick off this weekend is a key match in deciding this season's title. (Note - data is for Celtic after 18 games and Rangers after 19 games). 
Clear Progress For Rangers Despite Right Wing Reliance
Rangers have managed to bring themselves within three points of Celtic but December has in some ways felt like a tough month for them. A disappointing loss in Vienna led to elimination from the Europa League. The domestic schedule got busy and they picked up some injuries. They managed to score more than one goal in only two of their seven SPFL Premiership matches. Those matches included draws with Hibernian at home and also away to bottom team Dundee. Narrow victories over Hamilton and St Johnstone weren't really of the expected standard either. Steven Gerrard has been quick to point this out himself. Perhaps mindful of the currently developing, childish spat between Hearts manager Craig Levein and Aberdeen manager Derek McInnes he was keen to stress that he didn't mean any disrespect to St Johnstone when suggesting that Perth was a place Rangers should not struggle to win in. The truth though is that these were all games Rangers perhaps should have won comfortably. The encouraging thing is that their underlying numbers do show positive indications about how they are performing. 
Rangers have an average expected goals per match of 1.64 and an average xG Conceded per match of 0.83. That puts them solidly in second place in the table in terms of xG difference and progress is clearly being made on both sides of the ball. They generate these numbers by taking a whopping seventeen shots every game and conceding just under ten attempts at their own goal. Alfredo Morelos, the twenty-two year old Colombian centre forward, takes around a quarter of those shots and is top scorer in the league with twelve goals. He has had a fantastic season so far and is key for the team in terms of hold up play, rolling opposition centre backs and combining with teammates on the right flank. 
That right flank is very important for Rangers. The dominance of right back James Tavernier and right winger Daniel Candeias in terms of deep ball progression and key passes shows where most attacks originate from. Tavernier incredibly already has eight assists this season and both he and Candeias have great delivery from wide areas. However, this can lead to Rangers being a little predictable at times when in possession. The midfield lacks both a goal threat and a creative passer. Ovie Ejaria and Lassana Coulibaly have disappointed. Liverpool loanee Ejaria hasn't provided the ball progression that was expected and Coulibaly has made basic short passing errors too often. Coulibaly makes the most passes within the Rangers squad that lead to the recipient being under pressure despite being only the eighth highest in the squad for being passed to when he is under pressure. Scott Arfield has performed well and combines well with Morelos but seems likely to miss this match due to injury. Longer term injuries to Jamie Murphy and Ryan Kent have also robbed Rangers of a significant threat on the left wing. This has been compounded by injuries to first choice left back Borna Barisic. Usual replacement Jon Flanagan does not provide much of an attacking threat and has also looked uncomfortable defensively at times too. 
The areas behind both full backs, particularly when Tavernier has joined the attack, can lead to opposition chances against Rangers. Their defensive numbers are improving but at times they have had to be bailed out by some incredible shot stopping by goalkeeper Allan McGregor. There have also been some inconsistencies in terms of the central defensive partnership. While Gerrard seems to be firmly wedded to a 4-3-3 formation he has chopped and changed personnel throughout the season. Some of this has been enforced due to injuries and a punishing fixture schedule but in defence he has seemed unsure of his ideal pairing. Although Connor Goldson made an error for St Johnstone's goal a week ago it has to be hoped he has recovered from the knock sustained on Boxing Day against Hibernian as he and Joe Worrall have been an effective partnership recently.
Title Winning Numbers But Questions Over Ball Progression For Celtic.
Celtic are managing to take almost twenty shots every game this season. They are limiting their opponents to less than seven attempts at their own goal. The Hoops are averaging 1.97 xG per match and conceding just 0.45 xG on average. Although they did have a blip in mid December, losing to Red Bull Salzburg and Hibernian, they have been very impressive recently. Rodgers' team has only conceded one goal at home since October 20th. They've scored three or more goals in four of their six league matches in December. Although Rangers are just three points behind Celtic still look favourites to win the league. 
Filip Benkovic has been a key part of Celtic's strong defensive performance. He and Dedryck Boyata have formed a formidable partnership since the Leicester loanee replaced the then injured Kristoffer Ajer and the underperforming Jack Hendry. A concern for Celtic is that left back Kieran Tierney may miss this match through injury. The young star is a significant loss both in terms of the ball winning and ball progression he provides for the side. Tierney's usual replacement, Emilio Izaguirre, was substituted at half time in Celtic's most recent match after giving up a penalty following being repeatedly exposed by passes in behind him. Given the importance of the right flank to Rangers either Izaguirre or his own replacement Jonny Hayes is in for a testing match. Right back Mikael Lustig is a capable defender and goalkeeper Craig Gordon is a fine shot stopper but both do limit Celtic in an attacking sense. Gordon's distribution can be poor and Lustig, now aged thirty-two, doesn't get into advanced areas enough to help Celtic overload opponents. 
For some of the second quarter of this season Celtic played Callum McGregor in the 6 position instead of Scott Brown. This helped quicken ball progression, removed some of the onus on their centre backs to break the lines and gave more of a creative passing threat from the centre of the pitch. Brown is back in the team now and is a great source of aggression, tackling and experience. In the most recent match against Aberdeen his return did lead to centre backs Benkovic and Boyata being the main, and largely ineffectual, outlet for ball progression as the opposition sat deep from the start of the second half. It will be interesting to see if this continues against Rangers. 
Other options in midfield include Ryan Christie and Olivier Ntcham. Ntcham can be wasteful with long shots - he's not responsible for all of those outside the box efforts shown above but it is close! However, he makes almost double the number of deep progressions compared to every other Celtic player. His ability to bring the ball into dangerous areas might mean Rodgers will recall him to the starting lineup and he did score the only goal the last time Celtic met Rangers. In the absence of a threat from full back and with Tom Rogic unavailable due to international duty Celtic will need James Forrest and Scott Sinclair to focus on getting behind the opposition in wide areas. Forrest's goal flurry earlier in the season and Sinclair's hat-trick in the last match were impressive but much will depend on the service they get to centre forward Odsonne Edouard. The twenty year old Frenchman showed against Aberdeen that he has the quality to decide matches but does need help to generate more shots.
Must Win Match Could Be Decided By Centre Forwards
Although there are significant injuries for both Rangers and Celtic each will feel that this is a match they can and must win. Rangers might consider following the lead of Red Bull Salzburg and Hibernian by using a 4-4-2 diamond with the forwards splitting wide out of possession to pin back Celtic's full backs and a capable presser such as Daniel Candeias marking Celtic's deepest midfielder. Throughout this season the average distance from their own goal at which they are making aggressive actions has increased for Rangers. This gradually higher press is working judging by their underlying numbers but do they have the confidence to continue that against Celtic while not giving away too many fouls and picking up too many cards? Brendan Rodgers is undefeated against Rangers with ten wins out of twelve matches. Can this continue given possible personnel issues at left back? Can his attacking midfielders get in behind Rangers' fullbacks? 
The two key figures on the day may be centre forwards Morelos and Edouard. Rangers need to set up better chances for Morelos and Celtic need to set up more chances for Edouard. If this happens then either youngster may have a decisive role in the Scottish title race.