Two defensive lapses in the opening 11 minutes effectively cost us a game that we largely dominated.
Antonio Valencia was the first to capitalise, seizing on a loose pass to beat Sead Kolasinac to the ball. Valencia switched passes with Paul Pogba and, with defenders drawn to the Frenchman, Valencia had room to squeeze a shot under Petr Cech.
It got worse. Shkodran Mustafi gave the ball away under pressure from Jesse Lingard, Romelu Lukaku fed Anthony Martial and he laid the ball into Lingard’s path for a crisp finish in off the far post.
To compound matters, Mustafi was unable to continue. On came Alex Iwobi as Arsene Wenger reverted to a back four.
United were happy to sit deep and hit us on the break, and indeed they did look ominous when they counter-attacked at pace through Pogba, Lingard and Lukaku. But the extra attacking option allowed us to pour forward and create chance after chance after chance.
Fourteen shots rained in on David De Gea’s goal in the first half alone and he rose to the challenge, saving impressively from Hector Bellerin, Alex Lacazette and even Lukaku.
At other times fortune deserted us - Lacazette was particularly unlucky with ricochets inside the six-yard box - and there were glorious chances missed by Granit Xhaka and Aaron Ramsey, the latter denied by a wonderful block from Nemanja Matic.
Lacazette did halve the deficit early in the second half, firing past De Gea after Alexis had picked out Ramsey’s run into the box and the Welshman had sensibly laid the ball back for our top scorer.
The tide had turned but we were hit by a suckerpunch as we chased an equaliser. United broke and Pogba got past Koscielny to square the ball to Lingard for a tap-in.
Pogba was sent off for a dangerous challenge on Bellerin and we laid siege to the United goal for what little time remained.
But Danny Welbeck had a strong shout for a penalty turned down and ultimately our attacking verve was not reflected by the scoreline.
We were left to rue those mistakes.
HOW IT HAPPENED
CHANCE AFTER CHANCE
Fourteen shots in the first half and eighteen more in the second half, but just the one goal. Here’s the best - or worst - of those near-misses:
20 - Xhaka’s header back into the six-yard box finds Lacazette but, on the stretch, he can’t get power on his shot. The ball bounces off De Gea, hits Lacazette again and rolls agonisingly wide
30 - Ozil clips a free-kick over the wall but Ashley Young has the presence of mind to drop off and head the ball clear from inside the six-yard box
32 - Lacazette is first to a loose ball, De Gea gets something on his shot and the ball clips the crossbar. Iwobi is crowded out from the rebound but the ball rolls to Xhaka - who fires wide
36 - Lacazette chips the ball up for Ozil to hit on the run from the edge of the box. It’s straight down the middle and into De Gea’s hands
42 - Koscielny keeps the ball alive following a corner and Matic brilliantly blocks from Ramsey firm shot
44 - De Gea makes a flying save to stop Bellerin and then gets down to deny Kolasinac
45+2 - Lukaku inadvertently diverts a free-kick towards his own goal but De Gea makes a brilliant save
56 - De Gea makes a sharp stop to deny Lacazette and then blocks Alexis’ follow-up from point-blank range
WHAT IT MEANS
This result means we drop back to fifth place after 15 games of the Premier League season.
Liverpool have moved above us after their win at Brighton, but we’re still three points clear of sixth-placed Tottenham.
We face BATE Borisov in our next game, in the Europa League at Emirates Stadium, and travel to St Mary's on Sunday afternoon to play Southampton in our next league fixture.
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