Arsenal's chances of qualifying to the last eight of the Champions League for the first time since the 2009/10 campaign took a big hit following their 1-3 defeat against AS Monaco in the first leg of the round of sixteen at the Emirates on Tuesday.
Geoffrey Kondogbia opened the scoring in the closing stages of the first half, before former Tottenham and Manchester United striker Dimitar Berbatov added another after the break.
Alex Oxlade-Chamberlain managed to pull a goal back in injury time, but Yannick Ferreira Carrasco again restored Monaco's two goal lead by scoring right at the death.
The game started with Arsenal looking very positive as Danny Welbeck got a very good opportunity after only two minutes. The former Manchester United striker, after breaking away from Elderson, moved into a very dangerous position, but his angled effort was not on target.
The Gunners got another chance through Olivier Giroud in the 24th minute, but the Frenchman header, following a corner, was off target.
The best chance of the first half fell to Alexis Sanchez, who advanced into a very good position after exchanging some good passes with Mesut Ozil. The Chilean tried his luck from 18 yards out, but his effort was just over the crossbar.
The hosts were made to pay for their missed opportunity as Monaco finally broke the deadlock in the 38th minute. Arsenal defenders failed to close down Kondogbia, and the Frenchman fired a 25-yard effort that zoomed past David Ospina after taking a thick deflection off Mertesacker.
Right after the break, the Gunners got a very good chance to level the scores when Sanchez raced ahead from the right flank before sending an excellent cross towards Giroud at the near post. Everyone thought the Frenchman would score, but the striker, after failing to adjust his feet on time, stabbed the ball wide.
Giroud was again seen beating the turf in frustration in the 52nd minute, after he missed another good chance by heading an excellent free-kick from Santi Cazorla over the crossbar.
The miss proved to be very costly as the visitors doubled their lead through Berbatov in the 53rd minute.
A quick counter attack saw Anthony Martial advance from the left and square the ball towards Berbatov, who showed great composure to hold off the Gunners' retreating defence, before slotting the ball clinically past Ospina.
Giroud, who was clearly not having the best of nights, missed another sitter in the 57th minute as he blasted an effort over the crossbar from only eight yards out, right after Sanchez had forced a good save from Subasic .
Monaco nearly went further ahead right after the hour mark when Moutinho picked out Martial with an excellent pass on the left. The Frenchman unleashed a good shot from a tight angle, but Ospina was able to keep out his effort.
Meanwhile, at the other end, Walcott, after managing to latch on to an excellent through ball from Sanchez, forced a good save from Subasic in the 64th minute. The rebound fell to Welbeck but the England striker's follow up hit Walcott's leg and flew over the crossbar.
Arsenal were finally able to pull a goal back in the first minute of added time through substitute Oxlade-Chamberlain. Fabinho defensive header, following Ozil's cross, went straight towards the England forward, who found the nets with a fantastic curling effort that flew past Subasic into the top corner.
Boosted by the goal, the Gunners started pressing for an equaliser, but they were dealt with another blow as Carrasco restored Monaco's lead in the fourth minute of added time.
Bernardo Silva, after pinching the ball off Oxlade-Chamberlain, released Carrasco with an excellent through ball and the Belgian raced ahead before firing a good effort that went in after taking a deflection off the far post.