Daniil Medvedev, in his first match since clinching the world number one ranking, beat Japan's Yoshihito Nishioka 6-2 6-3 in Acapulco on Thursday to reach the semi-finals of the ATP 500Daniil Medvedev beats Yoshito Nishioka to reach Acapulco semi-finals event where he could next face Rafa Nadal in an Australian Open final rematch.

Medvedev, who took the court hours after Novak Djokovic's quarter-final loss in Dubai meant the Russian would replace him atop the rankings, converted six break points and fired down 12 aces, including one to seal the match.

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"It's not easy, actually, to play a match when you get this (news) during the day," Medvedev said during his on-court interview when asked about becoming world number one.

"Actually to be honest, Novak's match, I saw that he was losing, but I didn't know that if he loses I'm gonna become number one. I thought I have to do something big here.

"So then when I was receiving all the messages, well I understood that, yeah OK, it's gonna happen."

After blitzing his way through the first set, during which he converted all three break point chances and won 80% of his first serve points, Medvedev was forced to rally back in the second after falling behind 3-1.

Up next for Medvedev, who is the first player to reach the last four at Acapulco, will be the winner of Thursday's later match between Australian Open champion Nadal and American world number 39 Tommy Paul.

In January, U.S. Open champion Medvedev won the opening two sets against Nadal but the Spaniard stormed back to claim a record 21st Grand Slam title.

Medvedev said it would be special to face Nadal again.

"Kind of a chance to get my revenge," said Medvedev. "You have to learn from the best, which is him, Roger (Federer), Novak, Andy (Murray) ... always when they were losing a tough fight, they were trying to get their revenge.

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"Sometimes they managed to win, sometimes not, and that's what I going to try to do if I play Rafa."

World number four Stefanos Tsitsipas, who was runner-up in Acapulco last year, also reached the semi-final with a 6-3 6-4 win over American Marcos Giron and has not dropped a set this week.

Tsitsipas will face either British sixth seed Cameron Norrie or German lucky loser Peter Gojowczyk, who reached the quarters on a walkover after Alexander Zverev was kicked out of the event for his assault on an umpire's chair.