Greek Stefanos Tsitsipas said his recent form was simply "not good enough" as his poor run continued with yet another early exit from Flushing Meadows on Wednesday when Swiss qualifier Dominic Stricker stunned the seventh seed in the US Open second round in a five-set thriller.

Tsitsipas reached the Australian Open final this year but has never made it past the third round in six main draw appearances in New York and he struggled against Stricker's massive serve and booming forehand before bowing out 7-5 6-7(2) 6-7(5) 7-6(6) 6-3.

He won in Los Cabos earlier this month but his form dipped in the run-up to the U.S. Open, suffering early exits from Toronto and Cincinnati.

"I won't blame it on anything. It's just poor performance after Los Cabos," he said.

"I consider myself a good player, and I don't want to be a person that can be beaten easily or I'm giving my opponents easy time on the court against me. I try to make it as hard as I can, and if it doesn't work, it doesn't work. I move on with my life."

He removed his father, Apostolos Tsitsipas, as head coach earlier this month but said that shake-ups to his team were not to blame.

"By no means I'm supposed to put any blame on any people or any members of my team," he told reporters.

"Everything on court is under my control and under my talents, and the way I can play this sport are shown out on the court. If I'm not able to deliver, then I'm not supposed to be doing well."

His defeat marks the latest Greek disappointment in Flushing Meadows after eighth seed Maria Sakkari lost in straight sets in the opening round of the women's draw on Monday.