Aslan Karatsev said you need to be at "200 percent" if you want to beat Novak Djokovic, as he did in Belgrade last week.
The Russian is having a memorable 2021 so far, with him surging up the rankings and reaching the Australian Open semi-final.
Perhaps his finest achievement came on Saturday, though, when he not only beat Novak Djokovic, but did it in the world number one's own back yard at the Serbia Open.
When asked how he managed to pull it off, though, he said there was no secret: you just have to be absolutely perfect.
"I stepped on the court to win," Karatsev said of his memorable semi-final win over Djokovic.
"I was believing [in myself], and I said to myself that I would play every ball no matter what.
"I tried to keep this strategy that we spoke about with the coach. You have to fight for every ball, that was the key to success."
"It was a long, tough match against a tough opponent. You have to put in like 200 per cent to beat this guy, it’s like playing against a wall.
"And he also made some good shots. He doesn’t give you any free points. He always makes you play and you have to be always there because once you miss a couple of shots, he just takes it very quickly. That’s how I lost the second set."
Karatsev was unable to convert that outstanding win into a title, though, as he lost to Matteo Berrettini in the final.
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