Very harsh criticism lately. Ruthless articles about him everywhere I look. 
He had a great start, missed a penalty and he obviously couldn't stop thinking about it. But overall, it was a decent performance in the first half. 
He should have been brought off in the second half, yes. But apparently, Chamberlain picked up a knock and had to be subbed. And that was the last sub. The result was some very disappointing defensive work from him but he was hardly bought to play like a second fullback. He tried but he couldn't deal with all the overlapping because his mind was obviously elsewhere. So yes, in that sense, he bottled it. 
He's not been a disappointment in big games for Arsenal though. In fact, he's shown some signs of returning back to top form lately. Excellent performance against Liverpool just a few days ago.