We suffered a late defeat at Stamford Bridge on Saturday to leave Unai Emery still looking for his first points in charge.
The winning goal came nine minutes from time, undoing all the good work from a pulsating opening 45 minutes, when we struck twice in four minutes to level up after a disastrous start.
The first half was non-stop action. Chelsea began positively in their first home game of the season, and were soon a goal to the good. The gaps in our defence were far too big, as Marcos Alonso burst free on the left and fed the ball into an unmarked Pedro to slot home.
Our defending was unconvincing, but we looked dangerous going forward, and Pierre-Emerick Aubameyang had a glorious chance to level but uncharacteristically blazed well over.
The mistake was compounded just seconds later when Morata ran on to another long ball and slotted past Petr Cech.
The mood was hardly helped by another wasted opportunity as Henrikh Mkhitaryan skied one, but the Armenian made amends when he tucked home a wonderful left-footed shot from the edge of the area.
We were revitalised, and four minutes later drew level as a dangerous cutback fell invitingly at the feet of Alex Iwobi to thump home.
The half-time interval seemed to halt our momentum. Chelsea enjoyed more possession after the restart, and created more chances, but our defence were far more compact.
That was until substitute Eden Hazard escaped down the left wing and picked out Alonso at the near post to tuck home the winner.
HOW IT HAPPENED
It's back home for another London derby next Saturday, this time against West Ham, with an early return to Emirates Stadium for Jack Wilshere.
Then it's Cardiff away before the first international break of the season, and time to take stock four games into the Emery era.
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