Liverpool's Chance Quality
There has been a lot of debate amongst the analytics community on Twitter recently, regarding how chances created vary in quality.
Whilst there is no surprise in that, when you look at a pitch map of them on Stats Zone, it’s clear that the quality varies greatly. Take a look at Liverpool's chance creation map from the recent victory over Manchester United:
As an aside, it's very interesting to note that the pair of set piece chances created by Steven Gerrard's meet each other very close to the penalty spot; evidence of a deliberate tactic?
Anyway, back to the real issue here: chance quality. You can see on the above map a simple pass along the left touchline that doesn’t even reach the final third counted as a chance created.
This pass, by Jose Enrique, went to Raheem Sterling, who proceeded to dribble towards goal before having a shot. To my mind, the player creating the chance deserves little credit here, as there was so much to do before a decent shot could be taken. Just to clarify, as this was the pass to a player who had a shot, it has been correctly recorded as a chance created, as unusual as it may seem in this case.
I am therefore going to manually compile a record of the Reds' chances throughout this season, using a ranking system that I have devised, so that we can then see who is really the best at creating quality chances for Liverpool.
Clear-cut (or 'big') chance data covers the very best ones already, but since EPLIndex are no longer able to provide this to subscribers, it is not available in the public domain (to the best of my knowledge). My system will enable us to look at all chances in greater detail.
I don’t want to have lots of categories, else they’ll all contain small samples, so I’m proposing six different types of chance. Assuming that Liverpool create a similar number of opportunities as they did last season (546) then I should have around ninety chances per category on average.
I have used Paul Riley's SPAM model and Colin Trainor's Heat Maps as a guide when deciding the different types of chance, though as I will have to compile this information myself manually, I've had to simplify it slightly.
As an example, whilst Colin divides the wide areas of the box in to two sections, I’m going to struggle to maintain consistency of recording on that front whilst using Stats Zone. I am therefore going to stick to using pitch markings to divide my zones.
It should also be noted here that no record is made of whether or not the chance resulted in an assist, as that is not down to the chance creator. The six categories, and the points I will be awarding, are as follows:
Central Box Open Play (CBO), 5 points - Passes in open play that are received in the central area of the penalty box, which I define as the width of the six yard box reaching out from the goal line to the edge of the box (so the same as in the SPAM model, in other words).
Central Box Set Play (CBS), 3 points - These passes are received in the same area as the above, but receive fewer points as it's far easier to put the ball in to a specific area when striking a dead ball with all of your opponents at least ten yards away.
Wide Box (WB), 3 points - Again borrowed from SPAM, these are the areas within the penalty area that are wide of the six yard box.
Central Outside Box (COB), 2 points - This zone maintains the width of the six yard box, but covers the area from outside of the penalty box out to where the final and midfield thirds meet.
Final Third (FT), 1 point - The rest of the final third essentially, meaning outside of the penalty area, and beyond the width of the six yard box.
Outside Final Third (OFT), 0.5 points - The recipient of the pass will have to do remarkably well to score with one of these, as per the aforementioned pass by Jose Enrique against Manchester United. I was tempted to ignore these entirely, but felt I should give a minor acknowledgement to them as they will be recorded by Opta as chances created.
I'm not going to claim that this is a perfect system at all, and I gladly welcome any constructive feedback in the comments below, but hopefully it should help to move the 'quality of chance' debate along a little bit, certainly with regards to Liverpool at least.
I've already realised that crosses into the centre of the box will be ranked well even though they are usually hard to score from, but it is difficult to differentiate them from passes, and I am trying to keep this simple at present. This system will therefore make Stewart Downing look like a world beater, but that's a price I'm willing to pay for the time being!
With the categories decided, I am now able to compile the figures for Liverpool's first three league matches this season, to see both which Liverpool players created the best chances, and also how the Reds fared against their opponents overall on the day.
Let's look at the players first. I should point out here that for some reason unknown to me, the figures on Stats Zone and WhoScored differ. The latter note that both of the Daniels (Agger and Sturridge) have created a chance, but the former has no record of that. As I will be using the former exclusively for this project, don't be surprised to see more such discrepancies in future.
It's important to remember that if a player creates a lot of chances in poor areas, then it's almost certainly not their fault; they haven't made their team mate who received their pass shoot at goal, after all.
But we can see that from the above table that whilst Iago Aspas has created the most chances for Liverpool this season, too many have been in poorer areas of the pitch. As I say, that's not his fault entirely, but it does help to put his chance creation figures into better context for future reference.
Philippe Coutinho leads the chart here in terms of points per chance, though this research has revealed an interesting anomaly in terms of his creative powers this season.
Although his total of six chances is very respectable (with 2.0 per game currently joint eighteenth best in the Premier League), they were all created in the first sixty-five minutes of the match with Stoke City. In other words, the young Brazilian has now gone 205 minutes without fashioning a goal scoring opportunity. This will certainly be something to keep an eye on in the forthcoming weeks.
I have not compiled a player breakdown for Liverpool's opponents, but I can reveal how the two teams have done in creativity terms in the three matches so far:
For the teams, I have added a column for the percentage of all chances that find the centre of the box. As we can see with Stoke City, the majority of their best chances came from set pieces, and they won't be the only team to visit Anfield this season where that is the case, so it makes sense to acknowledge it.
At this point, I obviously have no idea if any of these figures are particularly good or bad, though I endeavour to compile all of last season's figures when I have the opportunity, in order to hopefully create some benchmarks. What I can say at this point is:
Liverpool created more chances against Stoke City than in the other two games combined by far, yet they were fractionally better chances on average in the Aston Villa game.
In their first game since Mark Hughes replaced Tony Pulis, the Potters were still very reliant upon set pieces to create their best chances, and have had the highest percentage of their chances in the centre of the box of any team here.
Although Manchester United had just one more chance than Liverpool at Anfield, overall their opportunities were 62% better. It should be noted though that Agger's assist for the winner was logged as a shot on Stats Zone rather than a chance, and it would've been a CBO to boot. By the same token, the Dane was trying to score rather than assist Sturridge though, so perhaps Stats Zone are correct.
This is my first attempt at this sort of analysis, so as I mention above, all feedback is very gratefully received. Thanks for reading.
Recent and related posts you might like:
Liverpool 1 Manchester United 0: Stats Zone Analysis - The first in a new series, looking at the key issues from a match by utilising the Stats Zone chalkboards.
What A Difference A Year Makes – The gulf between Liverpool’s form in 2012 and 2013 is quite remarkable…
The Creative Impact of Coutinho – The Brazilian is outperforming the Premier League’s elite level creative talents right now.
The Coutinho Conundrum - There is an interesting quirk in the young man's stats at present...
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