Greek tennis superstar Stefanos Tsitsipas has advanced to the semi-finals of the of the Western & Southern Open tournament following the retirement of Reilly Opelka because of an injured right knee.

In the tournament, an ATP Masters 1000 event, Mr Tsitispas prevailed over three of the tallest men in the ranks, Kevin Anderson (2.03m), John Isner (2.08m) and Opelka (2.11m).

“The question remains: Am I going to make it to the record books for playing the tallest players on the ATP consecutively, one after the other. I have to check it out. I don’t think it has ever happened before,” said Mr Tsitispas on the ATP Tour website.

He will meet the winner of the match between world number 3 Milos Rainoc and Filip Krajinovic of Serbia in the semi final.

Meanwhile on Tuesday, Maria Sakkari caused a sensation at the same tournament when she beat Serena Williams in three hard-fought sets to advance to the quarter finals which lost on Thursday to Britain’s Johanna Konta.

According to website, Ms Williams, blamed her cramping legs for her third-round loss to the Greek who is ranked 21 in the world.

“I don’t think that helps mentally, when you know the match is over and you won the match, and now your legs were always tired and now they’re even more tired. I put myself in a bad position,” said Ms Williams.

“It’s like dating a guy that you know sucks,” said 23-time Grand Slam winner who led 5-2 in the opening set before Ms Sakkari drew level. The match was then delayed by rain with Ms Williams taking the first set.

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In the second set, Ms Sakkari led 3-1 when Ms Williams reeled out three  games in a row to serve for the match.

But Ms Sakkari dug deep to recover and win the second-set tie breaker to force a third set to win 5-7, 7-6(5), 6-1.

“I knew it was going to be an ugly match from my side but I’m extremely happy with the result. She (Ms Williams) is a role model for me and many others. What she has achieved in our sport is unique and I don’t know if anyone else is going to do it again,” said Ms Sakkari.

The Western & Southern Open tournament which is usually held in Ohio was moved this year to Flushing Meadows the venue of the last Grand Slam of the year, the US Open. The tournament was played a no-spectator “bubble” because of the COVID-19 pandemic.