Arsenal blew a three goal lead at home to Anderlecht as they lost further ground to Borussia Dortmund in the race to finish top of their Champions League group.
The Gunners were cruising at 3-0 up before the Belgian side hit back to level the scores at 3-3.
The second goal was a penalty, conceded by Nacho Monreal in a farcical manner which summed up the brittle Arsenal defence.
The Spaniard is viewed as shaky even in his preferred position as left-back, but has had to play as a stand-in centre-back this season due to a lack of cover in the position, and Laurent Koscielny being out injured.
Arsenal have got away with picking Monreal in the position up until now, but this time they came unstuck.
Arsene Wenger has previously stated his desire to sign a defender in January, admitting not doing so previously was an error.
The contest with Anderlecht will only have reinforced his decision, and the defeat is a tough one in terms of the group. Borussia Dortmund are five points ahead of Arsenal with two games to go, and even a Gunners win will unlikely be enough to see them through as group winners, with the Germans really needing to lose their final game for that to happen.
Monreal took plenty of flak on Twitter as a result of his performance, but manager Arsene Wenger also had his fair share...
Monreal is not even conference level get him off— michael dewey (@dewey6) November 4, 2014
Play Chambers in CB Arsene and Bellerin RB. it's simple no need for Monreal#AFC— Abdullah.Gooner (@PUREGOONER90) November 4, 2014
Monreal is a fraud I want to see his football work permit— /fək 'siril/ (@FvckCyril) November 4, 2014
I seen enough of monreal you know. rather take my chances with bellerin— DILLYHU$$LE (@DillanAD) November 4, 2014
A big club like arsenal can attract many players and I bet at least one of those players is a better CB than monreal.— Michael (@MLovesArsenal) November 4, 2014
I'd rather have had Alexis at CB than Monreal. I've never liked him. He can't do anything. He's below average in all departments— _____ (@IGotMesutAndTie) November 4, 2014
I feel for Monreal. Having his career and reputation wrecked thanks to an inept manager. Not his faukt— Arsene clownshoes (@whatgap) November 4, 2014