I know xG is divisive but I have been asked recently two questions around the stat, so I thought I’d spend some of my precious time putting together some numbers for you.
Ahead of this article, an explanation of what ‘xG’ is courtesy of the Opta website – Expected goals (xG) measures the quality of a shot based on several variables such as assist type, shot angle and distance from goal, whether it was a headed shot and whether it was defined as a big chance. Adding up a player or team’s expected goals can give us an indication of how many goals a player or team should have scored on average, given the shots they have taken.
I’ve gone into this without prejudice, but I’ve been asked to provide details for the following two statements. The first: Lincoln concede less xG with Michael Bostwick in the team than when he’s out. Seems obvious enough, the point here is that we expect to concede fewer goals when a terrifying man is at the centre of our defence than when he leaves Jason Shackell and Cian Bolger doing the dirty work.
The second point I was asked to either prove or disprove was this: We’re more creative with Jack Payne in the side. In other words, we have higher xG when he plays than when he does not.
I know Jack Mulhall is someone who criticises these stats, so is Pete Summers, so I will lay down the caveat before I start. Some games are more open than others for reasons which are abnormal; the weather (Accrington), bad teams (Bolton and Southend), us being woeful (Oxford at home). These would be expected to skew the numbers I suppose, but overall the two players have played in some of these games and not others.
All stats come from Wyscout, as of 3pm this afternoon.
Let us start with Jack Payne because the numbers here do give us an indication of performance. Of our 34 matches, Jack has started 18, come on as a sub in five and not played in 11. I was asked to prove that with him in the side were are more effective, but sadly I cannot. In the 11 games he has missed we have an xG of 1.41, contrasting with 1.14 when he starts. For a layman, the game sin which he doesn’t play see us create better chances.
With Jack starting, we score 1.06 goals per game against 1.55 when he doesn’t start. The caveat here is that Jack played during the rather difficult period post-DC and prior to Michael coming in, but overall the numbers seem to back up the argument that he should currently be warming the bench.
There have only been two occasions where our team xG has exceeded 1.5 with Jack starting since MA took over, that being the draw at Wimbledon and 2-0 victory against Sunderland. It’s interesting to note that Jack’s last three starts have been Gillingham away (woeful), then Sunderland which we won 2-0 and Wimbledon where we should have won and he scored. Has he been hard done by, despite the figures? Possibly so.
I decided to contrast those with the number ten rival Jack has battled with, Jake Hesketh. I expected the numbers to back up Jack Payne’s inclusion and to a degree it does. With Jake in the side our xG is 1.18, with him out of the side (predominately the first few weeks of the season) it is 1.23, However, with Jake in the side, we score 1.43 times per game, against 1.14 whilst he is out of the side.
The numbers do suggest that, contrary to my belief, Jake Hesketh is stronger than Jack Payne in terms of affecting us scoring goals this season. The xG might not be better, but we appear to be more clinical as a strike force with Jake in the side.
On to Bozzy, because these results are a little surprising. The obvious expected outcome here is we concede fewer chances with the behemoth starting than we do when he is absent, right? It’s not strictly the case, although the numbers are very similar. When Bozzy starts, we conceded 1.18 xG, when he doesn’t start, 1.13. There isn’t a huge difference in the actual chances opponents get against us.
The big difference is in the goals we conceded. In 15 matches Bozzy has started, we’ve let in 17 goals, 1.13 per game. That’s about in line with the xG, but remarkably when he doesn’t play that changes. In the 17 matches he’s missed, we’ve conceded 23 goals, 1.35 per game. As expected, we do concede more when he doesn’t play.
That’s not the surprising outcomes though. As part of the data I collected, I also got a snapshot of goals for and xG when Bozzy plays and that is truly eye-catching. With Michael Bostwick in the side, our xG is 1.22 and we score 1.47 goals per game. Without him, our xG is 1.08 and we score 0.76 goals per game.
This really surprised me, because it hints at him being as integral to us going forward as anything. He’s missed 17 matches for us, including blanks against Oxford, Peterborough, Shrewsbury, Portsmouth, Gillingham, Ipswich, Portsmouth, Rotherham and MK Dons. even more surprising is that he also missed the 5-1 win against Bolton, making these figures more favourable than they should be.
We’ve been expelling the virtues of Bozzy this week, me on the dog walk and Lewis in his article, but at no point did we suggest that he was an asset to our attacking play. Perhaps his distribution is better than his other two defenders? Well, I checked that too (obviously).
In League One this season he plays 35.65 passes per game with an 81.6% accuracy, of which 4.11 per game are to the final third. Jason Shackell plays 39.1 per game, 82.5% of which are accurate and 4.43 of which are to the final third. Cian Bolger makes 34.4 per game, 75.5% of which are accurate and 4.35 of which are to the final third, so no, there is no suggestion Bozzy is ‘better’ at passing. In fact, of the three, Jason Shackell plays the most forward passes (17.79 per game) and with the best accuracy (71.8%) of all three.
Could it just be that when Bozzy is on the field, standards are driven? Could it be his leadership, his mere presence and how he breaks up play that helps us create more chances going forward? The stats for our goals for and xG when he plays are remarkable and perhaps go some way to backing up numbers, by finding something in there that you can’t prove directly; that we’re an infinitely better side with Michael Bostwick in the team in all areas of the field.
I await this article being picked apart in the comments!