Arsenal need to avoid complacency, heed Barcelona exit warning vs. CSKA Moscow
If the belief that a 4-1 first-leg victory represented a finished job had permeated the Arsenal camp, then events last night in the Champions League would have disabused any complacent players of that notion. Barcelona took an apparently impregnable 4-1 lead to Roma and were knocked out in spectacular fashion.
The chances of a repeat event two days later may be statistically unlikely but Roma's magnificent comeback was still a timely reminder to Arsenal that they can't afford to relax in Moscow. Indeed, their own recent history tells a similar story: 3-0 up after the first leg of the last-32 tie with Ostersunds, they conceded twice in two minutes in the home leg before Sead Kolasinac steadied the ship. Disaster was only just averted.
Still, things should be kept in perspective: it was clear from the first leg that CSKA aren't very good. The margin of victory should have been much wider and if reciting the age of their creaking defence became a tiresome cliche, it was nonetheless revealing. An Arsenal attack which is the most potent in the competition should have put the game completely beyond doubt.
Even so, CSKA scored once thanks to the brilliance of Aleksandr Golovin and could have had a few more themselves, so unconvincing was the defending on offer from Arsenal. It is clear that Arsene Wenger has a big problem here. Poor defending has hindered Arsenal's league results dramatically and even if they get past CSKA to reach the semifinals of the Europa League, having a dodgy defence will limit their chances of doing much else. If they draw Atletico Madrid in the last four, it will likely be fatal.
Being unable to construct a convincing defence is hardly new for Wenger: it is a problem which has followed him around to varying degrees since 2006. But at the moment it seems particularly acute.
The big positive of the weekend's win over Southampton was seeing Arsenal's attacking ranks gain even more confidence. As Pierre-Emerick Aubameyang continued his goal-scoring spree since signing from Dortmund in January, Danny Welbeck scored twice and claimed an assist and a rejuvenated Alex Iwobi was involved in all three goals. The attack, at least, is in fine form.
But the big negative of the Southampton win was being forced to endure one of the most clueless pieces of defending in any match this season, as Shkodran Mustafi made a terrible mess of a cross from the left, waving Shane Long through to score. There was no sugar-coating just how bad this was. Even the largely implacable Petr Cech lost it momentarily. The German was also responsible for CSKA's only goal in the first leg as his poor clearance set in motion the chain of events which led to Golovin scoring his free kick.
In fact, Mustafi's form has been so underwhelming this season that it seems almost certain that Arsenal will try to upgrade this summer. Sven Mislintat's first signing at the club, Konstantinos Mavropanos, was a centre-back and if reports are true, the head of recruitment has identified it as a problem position, casting his net far and wide to find the right man.
But next season is next season. And for the moment there appears to be no convincing alternative. Laurent Koscielny's return will be welcome for the second leg against CSKA but there are few genuine challengers for Mustafi's place alongside him. Club captain Per Mertesacker travelled with the squad to Moscow but hasn't played a second since Jan. 7 and the FA Cup shock at the hands of Nottingham Forest. Neither Rob Holding nor Calum Chambers has made a convincing case when circumstances have allowed.
All of which leaves Arsenal with a potential liability at the back, and it would hardly be a surprise if CSKA were to target Mustafi given he struggled so badly with the pace of forward Ahmed Musa in the first leg.
It almost certainly won't matter in this isolated context. Arsenal's lead should be enough to carry them through. And yet even a team as talented as Barcelona have shown what can happen if you come in undercooked against a highly motivated team roared on by their home supporters. Despite a 4-1 lead, there can be no room for complacency here.
Tom is one of ESPN FC's Arsenal bloggers. You can follow him on Twitter @tomEurosport