- Rafael Nadal wins first singles match since his Roland Garros triumph
- Roger Federer also reaches quarter-finals of Gerry Weber Open in Halle
- Jo-Wilfried Tsonga knocked out of Aegon Championships by Croatia's Ivan Dodig
- Tsonga fears he may have broken finger during defeat and could miss Wimbledon
Rafael Nadal and Roger Federer began their grass court seasons with straight-sets victories in the first round of the Gerry Weber Open in Halle, Germany.
Nadal, playing in his first singles match since winning the French Open at Roland Garros last week, cruised to a 7-5 6-1 win against Slovakia's Lucas Lacko.
The world number two, whose only previous visit to the Halle tournament in 2005 ended in a shock first round defeat to Alexander Waske, was relieved to come though the match after a gruelling clay court season.
"Every hour on court works well for me - on grass - because I don't have a lot of time to practice. I'm happy to be through, that's the main thing. In the second set I think I did everything better," said Nadal.
He will be joined in the quarter-finals at Halle by Federer, who beat Germany's Florian Mayer.
Home player Mayer put up a brave fight against the world number three, with Federer securing a solitary break in each set to seal a 6-4 7-5 victory.
Federer will play Canada's Milos Raonic in the last eight, while Nadal takes on defending champion Philipp Kohlschreiber of Germany.
In another Wimbledon preparation event, the Aegon Championships at London's Queen's Club, it was a miserable day for world number five Jo-Wilfried Tsonga.
The Frenchman suffered a shock first round defeat to Croatia's Ivan Dodig, during which he suffered a finger injury that could rule him out of Wimbledon.
"I think it's serious. I will have a scan, but it sounds very bad. I felt like I broke something or I strained it when I fell," Tsonga told reporters during his post-match press conference.
The Frenchman looked out of sorts in a 6-7, 6-3, 6-7 defeat to Dodig, who was making his debut at Queen's Club and is ranked at 69 in the world.