Gael Monfils says his performance during his first-round loss in Cincinnati was driven by frustration and a desire to change up his game because he was not playing well.

Monfils was accused of tanking during the second set of his 6-4, 7-5 defeat to Jerzy Janowicz, which lasted only about an hour because the Frenchman began playing points without taking much time in between and attempting ambitious shots.

"I was nervous for my injury and my level is not there," Monfils was quoted as saying by L'Equipe. "I can not at all do what I want. And the more I do the more frustrated I became, and the harder it is to produce."

During the second set, Monfils said he was looking to change his mood and tactics. "I tried to make it a little more fun, a little more confusing for the opponent," he said. "Doing different things."

The Frenchman said he has been working hard during training but hasn't played well since arriving for the North American hard-court tournaments. Monfils was the No. 14 seed in Cincinnati.