He has not been gone long, but when Alexis Sánchez returns for Arsenal, presumably at some point this coming Saturday, he will be rejoining a team transformed. When Alexis hobbled off at Carrow Road, Arsenal were about to drop points in the Premier League for the third successive match, and had dropped to fourth place in the Premier League. Yet since Alexis' injury, and the injury to Santi Cazorla, Arsenal have won 5 out of 6 in the Premier League, climbing to the top of the league, and beating Olympiakos 3-0 in the Champions League to advance out of the group stage. Furthermore, there is a new midfield, with Aaron Ramsey returning to his preferred central role, and Mathieu Flamini and Calum Chambers sharing holding roles.
In Alexis' absence, Mesut Özil has taken on even more importance as the matchwinner. He has been assisted, though, by the return of Ramsey to a central position, with whom he has an excellent relationship, and with the return of Theo Walcott from injury, with Walcott taking up a left-sided position to compliment Joel Campbell on the right. The result has been the recreation of the Mesut Özil/Aaron Ramsey/Olivier Giroud triangle, which focuses more on building on the left hand side, with Monreal in close support. The change is telling: against Manchester City, 52% of Arsenal's attacks were down the left hand side (20% middle and 28% right) whereas against Manchester United in October, 40% of Arsenal's attacks were down the right hand side (30% middle and 30% left). The positioning and movement of Campbell and Walcott adds to this: the left footed Campbell is more able to come inside, creating natural width for Héctor Bellerín. On the left, Walcott, although predictable in his movement, knows that his job is primarily to make runs behind, and lets Monreal, Özil and Ramsey get on with the important work of building, with Campbell and Bellerín available on the right hand side.
The return of Alexis complicates things a bit. The Chilean's best period of form for the club remains the fall of 2014, when, in the absence of Özil, he was the main man. There is no doubt that Özil and Alexis will form an excellent partnership, and the signs are promising. Yet, when Alexis plays on the left hand side, he tends to run behind less and try to create and dribble more; effectively adding chaos to Özil's control. Earlier in the season, that worked, as Arsenal had a clear right-sided bias.
Yet in recent weeks, with Ramsey and Monreal contributing more to the build up of play and feeding of Mesut Özil, Alexis' chaos may be too disruptive. On the right, Joel Campbell has the ability to come inside and shoot, or try and create, which he has done, notably against Olympiakos, while also working really hard in tracking and helping Héctor Bellerín. These are all aspects Alexis brings to his game, at an obvious world class level. Furthermore, it suits Arsenal more: if Walcott is on the left, Arsenal, through Ramsey and Özil can try and spring him behind, with Alexis offering a secondary, third-man run, which he seems to prefer to the run in behind.
So far, Alexis has primarily played on the left hand side, but with the balance of the side shifting in his absence, it might also make sense to tweak his role in the side. Furthermore, it would remove (with all respect to Campbell) the weakest player of the attacking five, and turn the right-wing, which is right now a slight weakness, into a strength.