The French midfielder came on as a late substitute in the first leg at the Emirates Stadium and conceded a penalty 47 seconds later.
While last night, at the Camp Nou, Flamini was handed a surprise start by Arsene Wenger but was subbed off before half-time after picking up a yellow card midway through the first half.
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After the match, Arsene Wenger confirmed Flamini had picked up an injury - although it wasn’t particularly obvious at the time - hence the reason for his early substitution.
But he didn’t join his colleagues in the dugout to watch the second half. Instead, he bizarrely opted to view the rest of the match on a television screen in the Camp Nou press room.
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Wenger didn't know where Flamini was
An image of Flamini watching on from inside the ground was posted on Twitter by the Mirror’s John Cross, who asked Wenger why the player wasn’t watching from the stands with his teammates.
“I didn’t know where he was,” Wenger admitted, per the Mirror, after the match. “I’m not sure he was allowed on the bench. He was injured. He had treatment after half-time.
"I wouldn’t say that on a night of great football that was the most important thing about the game.”
Arsenal had chances - but Barcelona were clinical
Francis Coquelin replaced Flamini before the break but was powerless to prevent Arsenal slumping to a 3-1 defeat.
The Gunners had their chances and took one through Mohamed Elneny five minutes after the half-time interval, but goals from all three members of the ‘MSN’ - Messi, Suarez and Neymar - sent Barcelona through to the Champions League quarter-finals.
Wenger praises the 'MSN'
"In the final third, Barcelona's passing accuracy and creativity is exceptional," Wenger was quoted as saying by BBC Sport.
"We played against a team who has the best strikers I have seen. The three together are absolutely exceptional.
"From nothing, they can create a chance, especially Messi. He didn't miss a first touch, no matter where the ball came from.
"At some stage in our sport, we must admire art and they have two or three players who transform normal life into art. I respect that and I believe it is pleasure as well. For me, is it suffering."
Arsenal now turn their attention back to the Premier League and face a difficult match against Everton at Goodison Park on Saturday lunchtime.
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