Top-seeded Roger Federer played his first match in more than a month on Thursday and advanced to the Mercedes Cup quarterfinals with a 6-4, 5-7, 6-4 victory over American teenager Taylor Fritz in Stuttgart, Germany.
The 34-year-old Federer, who missed the French Open with a back injury, was able to fight past the 18-year-old Fritz in a grass-court match that started Wednesday and was delayed by rain.
"It was very difficult, just as I knew before the match," Federer said. "I was more fortunate at the end.
"After such a long injury, you need to find your rhythm."
Federer, ranked No. 3 in the world, tied Ivan Lendl with his 1,071st win on the ATP Tour.
Second-seeded Marin Cilic was ousted by qualifier Radek Stepanek 7-6 (4), 7-5. Third-seeded Dominic Thiem edged Sam Groth 7-6 (3), 7-6 (2) and No. 4 Gilles Simon beat Jan-Lennard Struff 6-4, 4-6, 6-2.
Third-seeded Ivo Karlovic topped wild-card entrant Igor Sijsling 7-6 (4), 7-6 (5) and Adrian Mannarino beat qualifier Daniil Medvedev 6-4, 6-2.
In second-round women's singles action, two of the top four seeds were ousted.
Top-seeded Belinda Bencic rallied after dropping the first set to defeat Varvara Lepchenko 3-6, 6-3, 6-2.
In second-round women's singles play at the Aegon Open in Nottingham, England, second-seeded Johanna Konta and eight-seeded Christina McHale were upset.
Saisai Zheng ousted Konta 6-4, 7-5 and Tara Moore eliminated McHale 6-2, 6-2.