Arsenal suffered their first Champions League defeat of the season as they were beaten by Inter Milan at the San Siro.
The Italian side took the lead on the stroke of half-time as Hakan Calhanoglu beat David Raya from the penalty spot. The Gunners were penalised for a controversial handball from Mikel Merino.
Arsenal dominated large swathes of the second half but were really lacking a creative spark to find their way back into the game. But they were kept at bay by their stubborn hosts as the Gunners' worrying stutter continues.
Here are all of the talking points from the San Siro.
Even before kick-off in Milan, Arsenal were given a huge boost as captain Martin Odegaard returned to the Gunners' squad. After making an appearance in training and travelling to Italy, he was named on the bench.
It was certainly a welcome sight given how much they have lacked his creativity over recent weeks. And while he only got on the pitch for a matter of minutes at the end of the game, his presence will be well received.
The next port of call will be actually getting the Norwegian playmaker back into the starting line-up. And that will not come a moment too soon for Arsenal considering their stuttering form in the Premier League recently.
And despite being buoyed by the return of their captain, Arsenal endured a less than inspiring start in the San Siro. The hosts started by far the better of the two teams.
Inter could have taken the lead early on through Dutch defender Denzel Dumfries, who thundered an effort off of the crossbar. Calhanoglu also went close with a low effort that skidded marginally wide of the post. Arsenal soon settled down and found a foothold in the game but might consider themselves slightly fortunate not to have fallen behind earlier than they did.
After Manchester City were handed a controversial penalty in their 4-1 defeat to Sporting Lisbon for a contentious handball, the same happened at the San Siro. As Arsenal attempted to defend a free-kick, the ball flicked up and touched Mikel Merino's arm.
Inter players appealed for the decision straight away despite the Spanish midfielder being in such close proximity. The referee concurred and awarded the hosts the penalty. Turkish midfielder Calhanoglu claimed the ball and tucked it home past Raya to give his side the lead.
It wasn't just on the pitch that Arsenal were in the bad books of the referee. Mikel Arteta is certainly no stranger to a booking but his yellow card against Inter might be the most bizarre of his career.
As the ball looked to be going out, it bounced towards the Arsenal boss. But instead of letting it go past him, the Spaniard picked it up. The only problem was that it hadn't fully gone out yet.
Inter players were left furious but the referee did not deem the offence to be worthy of a red. After making an active effort to get his touchline conduct in check, this one will certainly annoy Arteta.
While it's not a full-blown crisis yet, Arteta and Arsenal really need to rally themselves if they want to make a success of this season. Back-to-back 1-0 losses does not make good reading for supporters, while it is even more worrying for their prospects of a trophy this campaign.
The Gunners now sit 13th in the Champions League table - and must find some consistency if they are to avoid the perilous nature of the playoffs. They're also seven points off the pace in the race for the Premier League crown.
Their defeat in Milan makes it just two wins in their last six games in all competitions - those two victories coming against Shakhtar Donetsk and Preston North End. With Chelsea on the horizon, it is not set to get any easier.