STUTTGART, Germany - Top-seeded Rafael Nadal opened his grass-court season with a hard-earned three-set victory over Marcos Baghdatis of Cyprus at the Mercedes Cup on Thursday.

The Spaniard needed 2 hours, 40 minutes to win 7-6 (5), 6-7 (5), 6-2 and book a place in the quarterfinals.

"The first match on grass is always tough," Nadal said. "He's a very good player and he'd already played a match."

Nadal had a bye into the second round. He will next face fifth-seeded Bernard Tomic, who cut short the comeback of German veteran Tommy Haas with a 7-6 (6), 6-2 victory.

"I need to be more aggressive, to return better, and to move better," Nadal said after his first match since losing in the French Open quarterfinals to Novak Djokovic.

Nadal was 4-2 down when he saved three break points. He took the first-set tiebreaker with a service winner.

In the second, Baghdatis hit some big forehand winners down the line and was steadier. But in the third, Nadal broke serve for 3-1 and stepped up his game. Baghdatis finished with 12 aces, and Nadal seven.

The 37-year-old Haas played his second match after missing more than a year with a shoulder injury. Tomic saved two set points and then won the first 11 points of the second set as he quickly broke Haas' serve twice for a decisive lead.

"I couldn't serve the way I wanted to," a frustrated Haas said.

German qualifier Mischa Zverev continued his good run, beating Andreas Seppi of Italy 6-2, 6-4 for a place in the last eight. Zverev will face second-seeded Marin Cilic, the U.S. Open champion, who beat Matthias Bachinger of Germany 7-6 (2), 6-3.