Medvedev marks rise to No. 1 with Acapulco win

The 26-year-old Russian rode a rollercoaster of emotions after learning he'd take over the top spot thanks to Serbian star Novak Djokovic's quarter-final defeat in Dubai hours earlier.

But he got the job done against Japan's Nishioka and booked a semi-final showdown with Rafael Nadal in a rematch of the Australian Open final.

"It's not easy actually to play a match when you get this (news) during the day," Medvedev said of maintaining his focus after learning he will supplant Djokovic atop the rankings on Monday.

Djokovic's 6-4, 7-6 (7/4) upset at the hands of Czech world number 123 Jiri Vesely ensured the Serb's reign will end.

"To be honest, I saw that he was losing, but I didn't know that if he loses I'm going to become number one," Medvedev said. "I thought that I had to do something big here. So then when I was receiving all the messages, well, I understood, OK, it's gonna happen.

"The first goal for me was to still win today, because I'm here to try to win every match I play.

"But it's definitely some great news."

Medvedev will become the first man since 2004 outside the game's "Big Four" of Djokovic, Nadal, Roger Federer and Andy Murray to occupy the number one spot.

He becomes the third Russian man after Yevgeny Kafelnikov and Marat Safin to ascend to number one.

Despite the distractions of the day, Medvedev needed just 70 minutes to dispatch Nishioka. 

The Japanese qualifier went up an early break in the second set, leading 3-1 before Medvedev won the final five games of the match.

"He's a tough opponent," Medvedev said. "He knows how to return, how to run, how to make some crazy shots when you don't expect it. I'm happy I was able to keep my composure to the end."

- Grudge match -

Medvedev has lost just eight games in his past two matches and his latest win gives him a chance to gain a measure of revenge against Nadal.

The Spaniard rallied from two sets down to beat Medvedev in the title match in Melbourne, claiming a record 21st Grand Slam singles title.

"It's always special to play against him," Medvedev said. "Kind of a chance to get my revenge."

Nadal improved his career-best start to a season to 13-0 with a 6-0, 7-6 (7/5) victory over American Tommy Paul.

Nadal had just two unforced errors and dropped just 10 points in powering through the opening set in 27 minutes.

But Paul pushed him in a second set lasting more than 90 minutes.

"I think I played one of the best sets since a long time ago," Nadal said of the first frame. "I played fantastic in the first set. In the beginning of the second I made a couple of mistakes, and then he started playing better and better. The set became a little bit crazy with a lot of breaks."

Paul broke Nadal to open the second set, but Nadal broke to level at 2-2 and launch a string of four straight service breaks.

Serving for the set at 5-4 Paul was broken.

Nadal saved two break points in the next game to lead the set for the first time at 6-5.

Nadal had two match points against Paul's serve in the next game, but the American managed to push it to the tiebreaker.

Nadal dropped the first two points of the decider but won four straight to take a lead he wouldn't give up.

In other quarter-final action, third-seeded Stefanos Tsitsipas of Greece beat American Marcos Giron 6-3, 6-4 to set up a meeting with sixth-seeded Cameron Norrie, who sailed past Germany's Peter Gojowczyk 6-1, 6-0.