New world No. 1 Daniil Medvedev defeated Japan's Yoshihito Nishioka 6-2, 6-3 in Acapulco on Thursday to storm into the semifinals of the ATP 500 event, where he will take on Rafael Nadal in an Australian Open final rematch.

Medvedev, who took the court hours after Novak Djokovic's quarterfinal 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.

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

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

It all happened on the same day that Russia launched a full-scale invasion of Ukraine that began with air and missile strikes on military facilities before troops and tanks rolled across borders from the north, east and south.

"Watching the news from home, waking up here in Mexico, was not easy," Medvedev said, according to the Associated Press (AP).

"By being a tennis player, I want to promote peace all over the world. We play in so many different countries; I’ve been in so many countries as a junior and as a pro. It’s just not easy to hear all this news .... I’m all for peace."

Up next for Medvedev is Australian Open champion Nadal, who made a blistering start against world No. 39 Tommy Paul but faced a second set fightback from the American amid increasing humidity to prevail 6-0, 7-6(5).

Medvedev squandered a two-set lead against Nadal in their previous meeting in Melbourne in January, allowing the Spaniard to clinch a men's record 21st Grand Slam title.

He will have to be in top form to beat Nadal, who is on a 13-match winning streak in 2022 – his best start to a season in his career at the age of 35.

"Everybody knows how difficult it is to play against Daniil," Nadal said. "I know I have to play at my highest level if I want to have any chance, and that's what I'm going to try."

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."

World No. 4 Stefanos Tsitsipas, who was runner-up in Acapulco last year, also reached the semifinals with a 6-3, 6-4 victory over American Marcos Giron and has not dropped a set this week.

Tsitsipas will face British sixth seed Cameron Norrie who lost just one game to hammer Germany's Peter Gojowczyk 6-1, 6-0 in the day's final match on the main court.

Gojowczyk had received a walkover to the quarters after last year's champion Alexander Zverev was kicked out of the event for his assault on an umpire's chair.

Djokovic flops

Competing in his first tournament of the season, and first since getting deported from Australia, Djokovic needed to at least reach the semifinals in the Emirates to try and stop Medvedev from replacing him at the top of the rankings.

But Vesely had other ideas as the left-handed qualifier improved his career record against Djokovic to 2-0.

Djokovic, who has spent a record 361 weeks as the world No. 1, said at the start of the tournament that he "would be the first to congratulate" Medvedev.

"I'm lacking a little bit of the match play. You can see that. I'm still finding the groove on the court," admitted Djokovic.

The 34-year-old also fears not being able to recapture the rhythm of matches, because his vaccination status could prevent him from competing consistently, is a concern.

"It is. The more matches I play, the more comfortable I get on the court," said Djokovic, who currently cannot enter the U.S. for next month's Masters 1000 tournaments in Indian Wells and Miami.