Arsenal had striker Olivier Giroud sent off as they slumped to a disappointing 2-1 defeat in their Champions League Group F opener at Dinamo Zagreb.
The France forward missed a couple of early chances before collecting two needless cautions in the first half.
Dinamo took the lead against the run of play with an own-goal from Alex Oxlade-Chamberlain after the ball bounced back off him past goalkeeper David Ospina, who had saved Josip Pivaric's shot.
After Giroud's dismissal on 40 minutes, Dinamo doubled their lead through a powerful header by Junior Fernandes.
Despite a late goal from substitute Theo Walcott, Arsenal were left to reflect on another frustrating European away performance.
Gunners boss Arsene Wenger, perhaps with one eye on Saturday's Barclays Premier League trip to Chelsea, made six changes from the team which had beaten Stoke, which included a start for Ospina
Arsenal started brightly as Giroud, preferred in attack to Walcott, saw an early header tipped over.
The English club, in Europe's elite competition for an 18th successive campaign, continued to dominate at the Maksimir Stadium, which felt the force of an earthquake measuring 3.2 on the Richter scale on Tuesday night not long after Wenger's pre-match press conference.
Dinamo had not lost in a formidable run of some 41 matches and last season became the first team to go unbeaten through a Prva Liga campaign.
However, the Croatians had never previously qualified for the knock-out stages of the Champions League, with a 15-game winless run in the competition proper and were yet to beat an English side.
The hosts remained on the back foot as Arsenal pressed, with Oxlade-Chamberlain next away down the right. The England midfielder crossed for Giroud, whose near-post header hit the post and rebound struck the goalkeeper on the line.
On 24 minutes, Dinamo went ahead completely against the run of play.
Pivaric was played into the left side of the Arsenal penalty area inside Mathieu Dubuchy. His near-post effort was saved by Ospina, but cannoned back into the net off Oxlade-Chamberlain.
Arsenal's evening got worse five minutes before half-time when Giroud was sent off.
The France striker, who had already collected an earlier caution for dissent, tripped Daniel Ivo Pinto, which gave Romanian referee Ovidiu Alin Hategan little option but to issue a second yellow card followed by a red.
Dinamo almost doubled their lead at the start of the second half when El Arbi Soudani glanced a header against the far post, with the rebound scrambled behind.
It was 2-0 on 57 minutes when Fernandes got above three Arsenal defenders to head home a left-wing corner at the near post.
Wenger had seen enough, and soon made a treble substitution as Walcott, who once scored a hat-trick for England here, Francis Coquelin and Joel Campbell all came on.
Walcott reduced the deficit on 79 minutes when he produced a cool finish after sprinting clear onto Sanchez's pass down the right, but there was to be no late drama despite some five minutes of added time.
TWEET OF THE MATCH
"The #WengerForever brigade are to blame for this nonsense. He's 5yrs past his sell-by date. Just embarrassing. #afc" - Piers Morgan is left frustrated again.
ARSENAL PLAYER RATINGS
David Ospina: 5 (out of 10)
Mathieu Debuchy: 4
Gabriel: 5
Laurent Koscielny: 4
Kieran Gibbs: 4
Alex Oxlade-Chamberlain: 6
Santi Cazorla: 5
Mikel Arteta: 4
Alexis Sanchez: 5
Mesut Ozil: 5
Olivier Giroud: 4
Subs
Theo Walcott: 7
Francis Coquelin: 5
Joel Campbell: 5
STAR PLAYER
Junior Fernandes. The Chile forward was a handful for Arsenal's defence all night with his pace and positive mindset. Showed great strength to leap through a crowded six-yard box and power home a header for the crucial second goal.
MOMENT OF THE MATCH
Having earlier seen two good chances missed, Giroud lost his cool to collect a needless second yellow card and leave his team up against it chasing a match they should have already been in complete control of.
VIEW FROM THE BENCH
Dinamo manager Zoran Mamic had warned his side would not be sitting back against the Gunners, and despite riding their luck in the opening exchanges, the hosts grew in confidence to execute that positive game plan - helped in no small part by Arsenal's inefficiencies at both ends of the pitch. Gunners boss Arsene Wenger, meanwhile, opted for half-a-dozen changes, aiming to freshen the starting XI up ahead of Saturday's trip to Chelsea. But on this evidence, he will have plenty more adjustments to make to find the right balance again.
MOAN OF THE MATCH
Olivier Giroud should have known better than to trip Pinto when already on a yellow card. Whether or not either caution was soft, in the Champions League you cannot afford to give the referee a decision to make.
WHO'S UP NEXT
Chelsea v Arsenal (Premier League, September 19)
Hajduk Split v Dinamo Zagreb (Prva Liga, September 19)
Source: PA
