Henrikh Mkhitaryan made his debut but ended up on the losing side as we let a lead slip in South Wales.
It was all going well enough when Nacho Monreal continued his purple patch with a predatory finish from Mesut Ozil’s sumptuous diagonal cross.
It was Monreal’s fourth of the season and his second in three games.
But we only led for a minute. Alfie Mawson stole possession and slipped a pass through for Sam Clucas, who applied a calm finish past Petr Cech.
The wait for Cech’s 200th clean sheet goes on and his day got a lot worse when he failed to deal with a backpass from Shkodran Mustafi.