1. Shkodran Mustafi
"NOOOOOOOOOOOOOOOO!" came the bloodcurdling cry from an Arsenal fan a couple of rows in front of the press box on Thursday night. He'd just seen Shkodran Mustafi slip at the crucial moment, allowing Antoine Griezmann to equalise and potentially end the Gunners' hopes of making the Europa League final. "What's he fallen over for?!" the enraged supporter shouted, as Griezmann raced off to celebrate while Mustafi lay prone on the grass.
We're pretty sure the centre-back didn't actually intend to fall over at the worst possible moment, but it was a moment that symbolised the German's time at Arsenal so far. Before his crucial slip, Mustafi certainly hadn't had his worst game against Atletico, but he was brought in two years ago to improve the Gunners' defence and has generally been unable to do that. In fact, Arsenal's defensive record has got worse over the last two seasons.
Mustafi had been heavily linked with a move to Inter last summer, and admitted recently that his current campaign "has been a bit like Arsenal’s - peaks and troughs". Arsene Wenger said just a few days ago that he still regards the 26-year-old as "a promising defender for the future", but with the Frenchman no longer in charge beyond the end of the season, a new boss may potentially look to upgrade at centre-back. Arsenal need players for now.
2. Laurent Koscielny
As captain, Koscielny's place might look safe – but he too could be vulnerable to changes if a new boss wants to build a new defence. The France international has been a mainstay in central defence for several years now, but hasn't been immune from errors: Atletico's equaliser on Thursday was less down to Mustafi's unfortunate slip, and more because Koscielny failed to clear in the first place.
If Arsenal want to return to the top, a new manager may see a complete fresh start in defence as vital. Koscielny is now 32, and it would be hard to see him getting into many of the other top defences in Europe right now. For that reason, the skipper may not be indispensable.
3. Granit Xhaka
Xhaka has been a regular in the Arsenal midfield this season, without always – or indeed often – impressing. Defensively he's sometimes caught napping, and his disciplinary record has also been poor: the Swiss enforcer has picked up 22 yellow cards and two reds in two campaigns at the club.
Against Atletico, the Gunners had 76% possession so Xhaka had less to do defensively, allowing him to utilise his passing skills and spread play. He largely did that well, but was never really incisive in quite the same way as Jack Wilshere. If Arsenal are to compete at the top level again, they need more in central midfield – both offensively and defensively. Xhaka, not offering enough on either front, could be under threat.
4. Danny Welbeck
Some suggested that Louis van Gaal might have made a mistake by selling Welbeck to Arsenal in 2014, but so far that doesn't really look to have been the case. True, a lot of that has been down to injuries, which have restricted his game time since moving to the Emirates - but 27 goals in four seasons probably wasn't the return that Arsenal would have been hoping for.
Against Atletico, Welbeck showed promise but couldn't provide the clinical finishing that is so badly required in a match like that. A first-half effort was saved by Jan Oblak, when he probably should have scored.
Perhaps there's always been the sense that, while talented, Welbeck is just a little bit short of being a regular goalscorer in a highly successful team. As the years go on, that perception sadly continues to grow. He's now 27, and Arsenal may need more in attacking areas if they're going to be transformed into title contenders again.
5. Jack Wilshere
Wilshere's future is potentially more complex than the four players already discussed. After a difficult couple of years, the midfielder was Arsenal's best player against Atletico, controlling the play and setting up Alexandre Lacazette's goal. The La Liga side were happy to pack central areas and force Arsenal to attack on the flanks: Wilshere was the one player who was still able to find gaps and slide passes into more central positions, creating a number of chances.
The 26-year-old could yet play himself into contention for the World Cup - his chances have been helped by injury to Alex Oxlade-Chamberlain, a player he can actually take inspiration from. His ex-team-mate has flourished under new management at Liverpool, after stagnating under Arsene Wenger at Arsenal. Wilshere is already showing signs of revival, and perhaps under a new boss he can kick on again and finally become the player he was always supposed to be.
Despite all of that, he still has reason to worry about his future. His contract is up this summer, and reports have suggested that Arsenal have made a 'take it or leave it' offer that he's not entirely content with. After how he played against Atletico, though, this would seem a strange time to let Wilshere leave. Get the best out of him under a new manager, and he could be pivotal to a potential Arsenal revival.
