Arsenal manager Arsene Wenger suggested that Alexandre Lacazette may have taken offence to the arrival of Pierre-Emerick Aubameyang at the club.
The French striker has scored nine goals from 29 appearances in all competitions this season, and now has competition from the former Borussia Dortmund star.
“For him, one against one with the goalkeeper, he is a good goalscorer,” Wenger said after Lacazette appeared off the bench and missed a good chance in Saturday’s 1-0 loss to Tottenham.
“He has gone through difficult periods before. He works hard in training, works on his finishing.
“I don’t know what happened, did he not touch the ball well? It can happen, it is a fraction of a second.
“Maybe the confidence is not at its highest because he has seen a competitor coming in for him.”
Harry Kane scored the only goal of Saturday’s north London derby at Wembley that left the Gunners sixth in the standings while Spurs go fourth.