So what's causing the drop-off in chance creation, and the increase in finishing? One major change that could explain part of it is the playing of Alexis Sanchez as a central striker this season. As this article shows, Sanchez has been a big reason Arsenal have scored more than their xG number would expect. But while the change to striker might have been good for him personally (particularly since he's in contract negotiations with Arsenal at the moment), I'm less sure it's good for Arsenal. The following table shows Arsenal's usage rates from last season:
|Player||Successful Passes||Total Passes||Unsuccessful Passes||Key Passes||Assists||Goals||Shots||Take-Ons||Take-On Success %||Unsuccessful Take-Ons||Minutes||Possessions Used||Usage Rate||Positive Outcomes||Negative Outcomes||% Positive|
Last season, Arsenal had a pretty fearsome attacking triumvirate of Sanchez, Giroud, and Ozil. Sanchez actually posted the highest usage rate in the league, but all three were quite high and used the ball efficiently. This season, their usage rates now look like this:
|Name||Successful Passes||Total Passes||Unsuccessful Passes||Key Passes||Assists||Goals||Shots||Take-Ons||Take-On Success %||Unsuccessful Take-Ons||Minutes||Possessions Used||Usage Rate||Positive Outcomes||Negative Outcomes||% Positive|
Note that Giroud isn't even on here; he didn't meet the 360 minute threshold I'm using as Sanchez has completely taken over his role. Sanchez's numbers are quite similar to last season, but Ozil is using a lot fewer possessions than last year. You can also see the percentage of possessions used with a positive result is down for just about everybody on the team, partly explaining why S/TOP is down for them.
The switch of Giroud for Sanchez probably has a part to play in Ozil's usage rate, the drop in shot volume and the uptick in finishing. Giroud is the prototypical target man who needs to be fed the ball. Sanchez, as the Ringer article makes clear, receives the ball outside of the danger zone and brings it in himself. As a result, Ozil has created a lot fewer chances: only 5 of Sanchez's 11 open-play goals have been assisted, and none have been from Ozil. Last season by comparison, Ozil assisted Giroud 6 times before the New Year. Moreover, because Sanchez was able to generate such high shot volume from the wing, that has to be replaced by some combination of Walcott and Oxlade-Chamberlain. Walcott is averaging about 3.1 shots per game and the Ox 2.6, both lower than the nearly 4 Sanchez was averaging last year from the position. That loss of shots and Ozil's reduced role are probably combining to reduce the number of shots Arsenal produce overall.
Arsenal's improved finishing can also be attributed to the switch. This is not because Giroud is an especially bad finisher, but because Sanchez has been out of his mind so far. However, one thing I have noticed while reviewing Sanchez's goals is how much he has benefited from things outside his control. For example, three of his first six Premier League goals came from rebounds or deflections from other shots. While finding space in the box is certainly a skill, the fact that the ball made it to him is almost entirely luck. Only 5 of his 11 open-play goals have been assisted, as in addition to the rebounds he has been able to profit from defensive errors (notably Gary Cahill in the Chelsea game). Partly as a result, a lower percentage of Arsenal's shots are being created by a pass this season, 75% down from 81% last season. The fact that Arsenal are converting their SOT at such a high rate when not creating the chances deliberately makes me think in the long run this is unsustainable.
Even though I think it's doubtful the change will prove useful to Arsenal over the long run, I do think it may do the trick against City. As Pep has been pointing out recently, we have struggled with second balls and our defense does make errors, and Sanchez's pace, trickery, and power make him the perfect candidate to exploit those flaws. His tendency to drop into midfield will also be a problem, since I don't see any of Fernando, Toure, or Aleix Garcia being able to stop him. Honestly, I think the best defense is ball retention here, so I would go with a lineup geared to maintain possession. That would probably mean Nolito up front and Toure/Fernando as a defensive midfield combo, as much as it sickens me to type those words. We'll see what Pep has planned in order to beat a Top 5 opponent for the first time this year.