Roger Federer does not expect an easy ride at Wimbledon this year as he believes rival Rafael Nadal will be "in great shape" for the tournament.

Federer returned to action for the first time since March at the Mercedes Cup on Wednesday as he came back from a set behind to defeat Mischa Zverev in a 3-6, 6-4, 6-2 win to reach the quarterfinals of the event.

The Swiss legend will also be playing at the Halle Open before Wimbledon takes place from July 2 to 15 next month. Federer will look to not only win his ninth title at SW19 but also regain his No. 1 ranking from Nadal.

Meanwhile, Nadal won his 11th French Open title last week but hinted at potentially missing out on the grass-court season in order to prevent injuries after a grueling clay season. The Spaniard also confirmed Wednesday he would be withdrawing from the Fever-Tree Championships at the Queen’s Club in London that takes place next week on the advice of his doctors.

"Queen’s is a great event, I have happy memories of winning the title in 2008 and I wanted to come back this year," Nadal said after announcing his withdrawal. "But it has been a very long clay court season for me with great results. I would like to say sorry to the tournament organizers and most of all to the fans that were hoping to see me play, but I have spoken to my doctors and I need to listen to what my body is telling me."

However, Federer expects him to participate in Wimbledon, picking him as a player who could potentially stop him from winning his 21st Grand Slam title while also crediting his ability on non-clay surfaces. Nadal has won Wimbledon on two occasions in 2008 and 2010, notably defeating Federer in the final of the former in what many regard as one of the greatest tennis matches of all time.

Roger Federer Roger Federer will be looking to win a ninth Wimbledon title next month. Pictured, Federer of Switzerland kisses the trophy as he celebrates victory after the Gentlemen's Singles final against Marin Cilic of Croatia on day thirteen of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club at Wimbledon in London, July 16, 2017. Photo: Clive Brunskill/Getty Images

"He’ll be in great shape for Wimbledon," Federer said of Nadal, as per Metro. "Otherwise I haven’t thought too much about who could be favorite. Rafa’s won Wimbledon twice, so he’s no one-trick pony. He’s become better from year to year. He’s playing more aggressive and better on fast surfaces. He’s not only the king of clay, he can play well everywhere."

Federer also mentioned other names likely to cause problems at Wimbledon, in particular, Novak Djokovic who has shown good form during the clay season, while he also hoped the likes of Andy Murray and Stan Wawrinka feature.

"Then you also have [Marin] Cilic, [Juan Martin] Del Potro and, I hope, Novak [Djokovic] will come back strong. He has already shown good tennis this year," Federer added. "I also hope that [Andy] Murray and Stan [Wawrinka] will come back."

But for now, the 36-year-old's focus will be on the Mercedes Cup as he awaits his quarterfinal opponent. Indian qualifier Prajnesh Gunneswaran takes on Argentina's Guido Pella on Thursday with the winner taking on Federer.