World No. 6 Stefanos Tsitsipas is seldom overshadowed on court.

Yet, the 6'4" Greek has spent this week looking up to his Western & Southern Open opponents.

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Tsitsipas has knocked off two towering servers—6'8" Kevin Anderson and 6'10" John Isners—in succession and will try to take his return game to new heights meeting 6'11" Reilly Opelka for a semifinal spot.

Facing a trio of titanic serves gives Tsitsipas unique insight on the question of which players owns the best first and second serve in tennis?

Tsitsipas cites John Isner as owning the most dangerous first serve and Milos Raonic as the most lethal second server in the sport.

"I've had a lot of trouble returning Milos Raonic's serve at the Australian Open," said Tsitsipas, who did not earn a break point in a straight-sets loss to Raonic in January. "I mean, it was very well deserved from his side because he played unbelievable that day. I was very upset I wasn't able to find solutions that day.

"His serve was really a weapon, caused a lot of damage. I would probably say either John Isner or Milos Raonic. It also depends on the day. I've played Isner at the Wimbledon Championships a few years ago. It was very incredible the way he served that day."



Tsitsipas suggests Hall of Famer Pete Sampras is one of the best pressure servers he's seen as well.

"I'm sure Pete Sampras had a great second serve," Tsitsipas said. "He would hit aces with it from time to time. I've not played him. I can't really judge or tell.

"I'm probably going for John Isner's first serve and Milos Raonic's second serve."

Photo credit: Australian Open Facebook