The Greek tennis star was beaten in four sets by Thanasi Kokkinakkis in the opening round at Flushing Meadows and is alarmed by a loss of form that has seen him endure a miserable time at all four of this year's Grand Slams and fall out of the top 10 in the world rankings.

Tsitsipas said: "I'm nothing compared to the player I was before.

"I remember myself playing when I was younger, playing with adrenaline on the court, feeling like my life depends on the match.

"And these things, I feel like they have faded off, and let's say my level of consistency hasn't been as big."

The star is desperate to recapture the "hunger" that has propelled him to two Grand Slam finals and allowed him to challenge some of the leading names in the sport.

Tsitsipas said: "I remember my concentration used to be at its highest, at its peak, back then, and that's something that I feel has dropped a little bit.

"I know it sounds strange, but I feel like I need the hunger to reproduce the hunger I had back then.

"And I'm not a person that feels alright and settles for normal stuff. Like, I really want to regenerate it and bring it back because it brought a lot of joy to my tennis when I was able to feel that way on the court.

"I really don't know why it has dropped the last couple of months. I would even consider it like one to two years I've been feeling that way. I guess I was just able to hide it a bit better and put it to the side a bit more."