Serena Williams has suffered a shock defeat at the WTA’s Western & Southern Open by Maria Sakkari who is through to the quarter-finals. 

The 38 year-old, who has 23 grand slam titles, lost in three sets 7-5 6-7 (5) 1-6 to the Greek world No 21. 

Williams revealed she was cramping during the game but managed to race to 5-2 in the opening set before Sakkari drew level.

The American trailed 3-1 in the second and in the third she double faulted four times in the second game as Sakkari took advantage and surged ahead 5-0.

Sakkari then sealed overall victory against the former No 1.

Williams said afterwards: "It's hard to play the way I have been playing and stay positive.

"And to play nine hours in a week is too much. I don't usually play like that, it's all new to me.

"It was tough. I literally should have won that match. There was no excuse.

"I started cramping, but I shouldn't have been in that situation. I don't think that helps mentally when it's like, you know the match is over and you have won the match, and now your legs were already tired and now they are even more tired.

“I literally put myself in this situation. You know, it's like dating a guy that you know sucks. That's literally what I keep doing out here. It's like I have got to get rid of this guy. It just makes no sense. It's frustrating.”

Sakkari said of her win: “It feels pretty good, because she has been a role model for me growing up, and obviously what she has achieved is huge. So it feels very nice.”

The 13th seed will next face Great Britain’s No 1 Johanna Konta in the quarter-finals later today.

The US Open is just round the corner which is the first major to be staged since the coronavirus pandemic. It is due to begin at Flushing Meadows in New York City on August 31.