Mesut Ozil struggled mentally after Arsenal were dumped out of the Champions League by Bayern Munich, according to Arsene Wenger.
The Germany international has come under close scrutiny in recent weeks with another frustrating show at the weekend in the 2-2 draw at home to Manchester City.
Gary Neville questioned Ozil's work rate and suggested he could be holding out "for a £270,000 a week contract" before committing himself to the Emirates.
However, Ozil grabbed the headlines on Wednesday night after a sparkling display with the opening goal - his first in nearly four months - in the 3-0 defeat of West Ham. He also assisted Theo Walcott's strike.
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"I feel that he is back physically. He is focused. I know him quite well," said Wenger reflecting on Ozil's struggles that followed the 10-2 aggregate defeat by Bayern on March 7.
"He was hit hard by us going out in the Champions League - it took some time for him to recovery mentally. He has really been focused in training in last few weeks.
"We live in world of extremes. We are always praised too much when it goes well and too much [criticism] when it doesn't."
The 28-year-old's contract expires in 2018 and there has been speculation he could leave in the summer, although Ozil said at the end of March he would hold talks over his future and decide whether or not to sign a new deal "soon".
Arsenal, fifth in the Premier League table, will look to secure back-to-back league wins for the first time since January when they travel to relegation-threatened Crystal Palace on Monday, live on Sky Sports.