Arsenal's defensive disorganisation is chronic.
One player who did have a reasonably solid game at the heart of Arsenal's back four, though, was goalscorer Shkodran Mustafi.
But Arsenal were nearly immediately ahead as Mustafi lost his marker, Sol Bamba, at Granit Xhaka's corner to head home powerfully for his first goal since March.
If Gunners fans hoped the end of Arsenal Wenger's reign would cure the brittleness of their team, they received a clear reminder in the Welsh capital that Emery has much work to do to add the requisite resilience to his side. The Greek defender has put Cech in worrying situations way too many times this season already.
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Mourinho will now face Lampard in the dug-out and the United boss admitted it was no surprise the Chelsea legend became a coach. That was Jose Mourinho's first trophy in English football.
There are no question marks on his shot-stopping ability but with Emery persisting with passing out from the back, surely it is time to offer Leno a chance to impress? Showed he can deliver a corner when setting up Mustafi's goal but sadly set up Cardiff's too with a awful attempt at a cross-field pass. Emery has denied talks of a rift with the star playmaker but he has yet to show he can make the most of the German.
It was claimed Ozil had stormed out of a training session when Emery urged him to try harder to adapt to his high-tempo pressing game.
There will still be no room for Lacazette as Aubameyang will continue as centre-forward, but after Emery's comments this week I think we will see Mesut Ozil back in the line-up but pushed out to the right-wing?
If Aubameyang's strike was impressive, Lacazette's 82nd-minute goal was more powerful. Ozil epitomised an Arsenal team often comfortable in possession, and was also at the heart of their counter-attacking game, linking well with Alexandre Lacazette and being involved in approach play for his team's second goal. His finish was a belter, topping off a fine performance.
Arsenal signed midfielder Lucas Torreira from Sampdoria this season.