Arsenal left themselves with work to do to reach the Europa League last 16 after slipping to a surprise 1-0 defeat away to BATE Borisov in the first leg of their knockout tie.
A shambolic pitch did little to excuse a drab Arsenal performance as they were made to pay for some early missed chances by Stanislav Dragun's header, before Alexandre Lacazette's late red card compounded their misery.
With no domestic fixture this weekend, Unai Emery named a strong Arsenal line-up, with only two changes from the side that won at Huddersfield on Saturday.
They almost opened the scoring inside two minutes when Sead Kolasinac, always the Gunners' most dangerous outlet, crossed for Henrikh Mkhitaryan, but Denis Scherbitski made a superb low block.
Mkhitaryan's delivery then flashed across goal, begging for a touch, before Lacazette headed over wastefully after more good work from Kolasinac.
After half an hour of Arsenal dominance, the home side offered their first warning when Nemanja Milic skimmed the outside of the woodwork with a near-post flick.
It was a warning that Arsenal did not heed, and when Dragun headed home on the stroke of half-time the cat was, if not amongst the pigeons, then certainly waiting to pounce.
Arsenal thought they had equalised when Lacazette sidefooted home from Kolasinac's cross, only to see the linesman's flag correctly raised.
Emery threw on Pierre-Emerick Aubameyang and Lucas Torreira to try and salvage the game, and Kolasinac went close again, lashing across the face of goal, before being sacrificed for Denis Suarez.
But without Aaron Ramsey and Mesut Ozil, the visitors failed to unlock the door to secure a crucial away goal, and must now overturn a one-goal deficit at the Emirates next week without Lacazette, who was given his marching orders for a wild elbow on Aleksandar Filipovic four minutes from time.
Starting line-ups, match highlights and reaction
BATE Borisov: Scherbitsky, Rios, Volkov, Filipenko, Filipovic, Baga, Dragun, Hleb (58), Milic (69), Skavysh (80), Stasevich
Substitutes: Yablonski, Berezkin (58), Dubajic (69), Simovic, Chichkan, Moukam (80), Bessmertny
Arsenal: Cech, Koscielny, Mustafi, Monreal, Maitland-Niles (68), Guendouzi, Xhaka (69), Kolasinac (74), Iwobi, Mkhitaryan, Lacazette
Substitutes: Leno, Lichtsteiner, Elneny, Torreira (69), Suarez (74), Aubameyang (68), Nketiah
Referee: Srdjan Jovanovic (Serbia)
