Calum Chambers last played for Arsenal in March, coming on for the final 4 minutes of Arsenal's 2-0 win at Everton (incidentally, the Gunners last away win). His last performance of note was when he came on for the second half against Leicester City, with his performance, particularly his passing from the back, crucial to Arsenal's comeback victory against the champions. Aside from that, Chambers started each of Arsenal's cup games, but has started only twice in the Premier League, playing in total, 315 minutes. What makes that figure bizarre is that Chambers has been fit the entire season, and played 1571 minutes for Arsenal last season. But since Gabriel joined in January 2015, Chambers has seen his playing time reduced remarkably. Of his 17 starts in the Premier League in 2014/15, 14 came before the Brazilian joined. Chambers has gone from being nearly first choice (perhaps even being overplayed) to not even being chosen on the substitutes bench, despite injury to Per Mertesacker and Laurent Koscielny throughout the season.
"Perhaps Chambers hasn't been good" is an argument that one finds on Twitter. Yet that doesn't bear any factual evidence. In his last two significant games in the Premier League, Chambers has been good. Before the match against Leicester, Chambers started against Bournemouth in the Premier League, and was adept in a midfield position. Yet despite that, he was removed for Mathieu Flamini the following matchday, and hasn't got a look in since--despite the obvious weaknesses of Flamini, and the less than impressive return to form of Francis Coquelin. A player of Chambers' ilk was obviously required in midfield, hence Mohamed Elneny's run of games in the first XI, but it took until March for Elneny to start in the league, despite Chambers' availability.
And despite Chambers' strong performance against Leicester, and despite numerous examples that the Gabriel-Koscielny partnership is not a strong one, Arsène Wenger chose that partnership against Manchester United. It was the very next league game after the win against Leicester, and Arsenal were awful, succumbing to a pathetic 3-2 loss. Two performances stand out--Gabriel, who defended abominably for the first two United goals, and Coquelin, who failed to cope with Manchester United's pressure, thus denying Arsenal the ability to maintain any sort of pressure.
What is particularly galling is this season in comparison with last. Chambers played well overall last season, especially as a centre back. He struggled at times at right back, but the manager apparently sees his future at either centre back or centre midfield. But having gone from being a trusted squad player, Chambers is now not even on the bench, making this season wasted, in terms of development. For a manager who is apparently gifted in terms of player development (and it is perhaps worth pointing out that the most recent success story, Héctor Bellerín, would not have been a story had it not been for injury to Mathieu Debuchy), Arsène Wenger has shown a lack of care for Chambers' future this season. Despite being a better player, and playing better, than Gabriel and Mathieu Flamini, Chambers has played an eight of their combined minutes (351 minutes for Chambers; 1762 for Gabriel and 1089 for Flamini). With Per Mertesacker not really capable of being a first choice starter anymore, Calum Chambers should've spent the last few months getting a look in at the position (and after all, Chambers has more top-flight experience than Gabriel, prior to this season). That he has not is an indictment on Wenger's plan for developing him, and if he is not guaranteed a trusted position in the squad next season, Chambers should really look to move, for his own sake.