Nadal beat Federer, the defending champion, 7-5, 6-7 (3), 6-3 Sunday to win his first Hamburg Masters.
It was a reverse of last year's final, when Federer won his fourth title in Hamburg and snapped Nadal's 81-match winning streak on clay.
"It was important to win because it was the last big clay-court tournament I never won," he said.
Before the final, Nadal had called Hamburg "Roger's Home," but he proved to be an inconsiderate guest.
Hamburg is one of Federer's favorite tournaments and that's where he broke into the top 10. Federer went into Sunday's final with a 41-match winning streak in Germany and a 9-0 career record in finals on German soil. His last loss in Germany was in 2003.
One week before the start of the French Open, the only Grand Slam that Federer is yet to win, Sunday's loss could not have boosted the top-ranked player's confidence, although he tried to look unconcerned.
"I wish I could have won but I don't think it changes much," he said.
Federer must be wondering, however, how he let a 5-1 lead turn into a 7-5 first-set loss and how Nadal managed to win seven straight games.
The momentum then changed and Federer won the next four, only to be forced into a tiebreaker. He won it, but once Nadal grabbed a 4-1 lead in the third, there was no comeback for the Swiss.
"I felt I played the right type of game from the baseline. I could have served a little better, it wasn't my best performance maybe. I have to go for big serves, he is a good return player. It was a fun match," Federer said.
Sunday's loss did nothing to improve Federer's worst season since he became No. 1 in February 2004. He had mononucleosis at the start of the year and already has seven losses for 26 wins. His only title so far came at a relatively minor clay-court tournament in Estoril, Portugal, and he lost in the Rome quarterfinals last week.
"I played three hours and I had no physical problems whatsoever, so that's good. I'll take two days' rest and hopefully I'll be ready for Paris, Federer said.
He has been overshadowed by Nadal and No. 3 Novak Djokovic. Both have three titles this year and Djokovic won the Australian Open, the Indian Wells Masters and the Rome Masters last week to lead the annual points race.
Nadal already is the undisputed king of clay and his wins this week over Djokovic to protect the No. 2 ranking in a memorable semifinal, and over Federer, certainly helped before he goes for his fourth straight French Open title.
"I am happy that I won and that I beat the No. 1 in the world and the best player of the year (Djokovic) and that should give me some more confidence for the French Open," Nadal said.
Since April 2005, Nadal has lost only twice in 110 matches on clay - to Federer last year in the Hamburg final and last week in Rome to Juan Carlos Ferrero, when Nadal was slowed by a painful blister on his foot.
