Earlier, Roger Federer struggled to beat Juan Monaco 6-3, 2-6, 6-4 in the second round.

Federer, who needs to win the French Open to complete a career Grand Slam, has gone four straight tournaments without a title — his worst stretch since becoming the top-ranked player in February 2004.

"It was a tough first match. Obviously he's a good clay-court player," Federer said. "I am glad I came through."

Playing under a canvas roof on the center court on a rainy and cool day, Federer broke Monaco for a 5-4 lead in the final set and then served out the match, converting his first match point with a service winner.

"The court was extremely slow in the wet conditions. It was a good hard-fought match, maybe that's what I needed. I got a chance at the end of the third set and I was able to use it," Federer said. "I haven't played that great in recent weeks. I just need to get back into match grove, pick up as many wins as I can before the French Open."

Federer will next play Juan Carlos Fererro, who converted his fifth match point to beat Marat Safin 6-3, 7-6 (15), after Safin had squandered five set points.

Nadal, seeded second behind Federer, cruised after clinching the first set. Nadal is looking for his tour-leading fifth title of the year.

"It was a tough first set. It was cold, rain, much different than in Rome, much slower," said Nadal, who won his third straight Italian Open on Sunday.

He next faces Igor Andreev, who beat Nadal in the Valencia Open quarterfinals on April 8, 2005.

"It's nothing special for me, but he is a very good player. He has an unbelievable forehand," said Nadal, who beat Andreev in three sets at the start of the year in Dubai, United Arab Emirates.

Andreev beat Philipp Kohlschreiber 6-7 (3), 6-1, 6-4.

Also, Carlos Moya upset 10th-seeded Tomas Berdych 3-6, 7-5, 7-6 (6), and 16th-seeded Lleyton Hewitt defeated Juan Ignacio Chela 6-2, 7-6 (3). James Blake, seeded eighth, defeated Arnaud Clement 6-2, 6-3.

Wednesday's match was Federer's first since he split with coach Tony Roche over the weekend.

"I was focused totally on the match. It's a good sign that I was focused on how to play, how to adapt to the conditions," said Federer, who intends to go to the French Open and Wimbledon without a coach.

Federer has won the Hamburg Masters in three of his last four visits. The Hamburg event is an important warmup for the French Open.

Federer improved his record on clay this year to 6-2. He had 44 winners against Monaco, who had 12. But Federer also had 12 more unforced errors with 38.