Juan Martin del Potro continued his successful comeback with a 6-2 6-3 quarter-final win over good friend Jeremy Chardy at the Delray Beach Open on Friday. The towering Argentine broke serve four times in the 80-minute win against the fifth seed.

“I’m surprising myself with the good tennis I’ve been playing,” del Potro said. “I’m still working to get back to my top level, if I can. But I’m really enjoying playing tennis again. I’m so glad to be able to play another match. It’s so nice to be in this stadium and have fans come and watch me play.

“Against Top 30 players, you can’t keep hitting slice backhands, so I tried to hit more two-handed backhands than yesterday. I’m still working on improving my backhand and staying with it in competition. It’s part of my recovery for my wrist.”

The powerful del Potro will face big-serving American Sam Querrey in the semi-finals. Querrey was pushed to the limit by countryman Tim Smyczek before prevailing 6-7(1), 7-6(4), 6-4. Smyczek was attempting to reach his first ATP World Tour semi-final.

“I tried to stay aggressive and hit through the wind,” Querrey said. “I probably had a lot of errors out there, but I tried to hit the ball through the court. Tim is a great guy, and I always want the best for my buddies. If he keeps playing well, he will have his chances.”

Dominic Thiem is playing the best tennis of his career.

After beating Rafael Nadal en route to the Buenos Aires title last week, the 22-year-old dismissed second seed David Ferrer 6-3, 6-2 to reach the semi-finals of the Rio Open on Friday night.

“It was one of the best matches I’ve ever played, for sure,” Thiem said. “I’m unbelievably happy to be able to maintain my form from Buenos Aires here in Rio.”

The youngest player in the Top 20 of the Emirates ATP Rankings surrendered the first service break of the match, but was nearly perfect the rest of the way to score his second Top 10 win in as many weeks. He broke Ferrer four times and secured the win in 73 minutes.

Next up for the rising star is Guido Pella, who needed two and a half hours to top Daniel Gimeno-Traver 5-7, 6-1, 7-5 and reach his first ATP World Tour semi-final.

Nadal was slated to face Alexandr Dolgopolov, but advanced to the final four without hitting a ball after the Ukrainian withdrew due to a right shoulder injury. He will take on Pablo Cuevas, who defeated Federico Delbonis 6-4, 7-6(4).

No. 4 seed Grigor Dimitrov, the highest remaining seed at the Delray Beach Open, was the first player to move into the semi-finals after downing eighth seed Adrian Mannarino 6-4, 7-5 on Friday.

In his third quarter-final appearance of the year, Dimitrov struck seven aces and took down last year’s semi-finalist Mannarino in 79 minutes. He is still in the hunt for his first ATP World Tour title of 2016 after falling in the Sydney final to Viktor Troicki.

Dimitrov’s next opponent will be Benjamin Becker or Rajeev Ram.

Fifth seed Jeremy Chardy will take on wild card Juan Martin del Potro in the evening session.

World No. 1 and four-time champion Novak Djokovic made a splash ahead of the Dubai Duty Free Tennis Championships on Friday as he took some time out from practice to enjoy an afternoon at the Wild Wadi Waterpark in Dubai.

The Serb was joined by his brother, Marko, and friends as they enjoyed some underwater fun and many of the water rides at the park, including Tantrum Alley and Burj Surj.

Earlier, Djokovic had visited Bab Al Yam restaurant at Burj Al Arab, where he was greeted by Chef Maxime Luvara, who helped the Belgrade native create his very own juice.

Djokovic is set to return to action for the first time since defeating Andy Murray in the Australian Open final last month. The Serb is chasing his fifth title at this ATP World Tour 500 hard-court tournament, having lifted the trophy in 2009 (d. Ferrer), 2010 (d. Youzhny), 2011 (d. Federer) and 2013 (d. Berdych). Last year he finished runner-up to Roger Federer.

Main draw play is set to begin on Monday in Dubai. Djokovic is joined in the strong field by Stan Wawrinka, Tomas Berdych and Feliciano Lopez, as well as stars of the Next Generation, Nick Kyrgios and Borna Coric.

Fourth seed Marin Cilic reached his first semi-final of the season as he defeated Andrey Kuznetsov 6-3, 6-4 on Friday at the Open 13 in Marseille.

The Croatian improved to a 3-0 FedEx ATP Head2Head lead over Kuznetsov as he fired 10 aces and won 81 per cent of his service points, claiming victory in just 66 minutes. The 24-year-old Kuznetsov was bidding to reach his first ATP World Tour semi-final and fell to a 0-7 mark in quarter-finals. He also missed out in the Doha quarter-finals in the first week of the season (l. to Nadal).

The 27-year-old Cilic is looking to reach the final of this ATP World Tour 250 indoor hard-court tournament for the second time, having finished runner-up on his last appearance in 2011 (l. to Soderling). The right-hander goes on to face either top seed Stan Wawrinka or Benoit Paire.

Nick Kyrgios hit top form as he stunned third seed Richard Gasquet 6-0, 6-4 in less than an hour to reach the semi-finals. In a dominant display, the 20-year-old Australian relinquished just six points on serve and fired 17 aces, breaking Gasquet three times from seven opportunities in the pair’s sixth meeting.

It was just Kyrgios’ second win over Gasquet, whom he also defeated 10-8 in the fifth set in the 2014 Wimbledon second round. The Canberra native will bid to reach his second ATP World Tour final when he faces either Tomas Berdych or David Goffin on Saturday. Kyrgios reached his maiden final last year in Estoril, finishing runner-up to Gasquet.