The move started on the left but Mesut Özil’s crossfield pass changed the direction of the attack. Theo Walcott moved it out to Oxlade-Chamberlain on the right and, turning inside César Azpilicueta, his left-foot shot was still rising as it flashed past Courtois.
Mourinho could reflect on the moment later in the first half when Loïc Rémy clipped in a beautifully weighted cross to pick out Ramires six yards from goal. Ramires overlooked the first rule in those positions to head the ball downwards, turning it over the crossbar, and on the far touchline an aggrieved Mourinho could be seen gesturing how it should have been done.
His changes at half-time, not only withdrawing Rémy but switching Ramires, Fàbregas and Willian into different positions, were another sign of his discontent but Chelsea continued to make the kind of basic errors that, if we are going to be generous, smacked of pre-season rustiness. Fàbregas had a chance late on to send a free-kick into the penalty area but did not even get it past the first man. Soon afterwards, Branislav Ivanovic played the ball back to Courtois and the goalkeeper miscontrolled it, conceding a corner.
Hazard has rarely been so ineffectual and Chelsea plainly have problems in attack if the injury issues that prematurely ended Diego Costa’s involvement last season are going to trouble him again. Costa’s fragile hamstring ruled him out here and Rémy was taken off after a first half in which he strayed into offside territory on four occasions. Radamel Falcao was given the second half to impress but if the Colombian is to reinvent himself as a grade-A centre-forward there was little evidence of it on this showing.
For Arsenal, the issue is whether Wenger persists with Walcott in attack at the expense of Olivier Giroud. Walcott was the one Arsenal player who disappointed even if it was his pass that contributed to the goal. Giroud replaced him midway through the second half and in the closing exchanges he and Santi Cazorla both had chances to extend the lead. Courtois denied them both but there was still plenty to encourage Arsenal’s followers, one of whom now carries a little red box containing a medal Mourinho does not want to see again.
Man of the match: Alex Oxlade-Chamberlain (Arsenal)