"It wasn't easy for him tonight," Nadal said. "I played a very, very good match, very solid and serious."
Nadal usually receives a trophy when he beats Federer. This time, the reward is a chance to play Novak Djokovic — No. 1 vs. No. 2 — for the title Sunday.
Djokovic stretched his winning streak to 25 consecutive matches by beating Mardy Fish in the other semifinal, 6-3, 6-1. Three-time Grand Slam champion Maria Sharapova seeks her first Key Biscayne title Saturday when she plays 2009 champion Victoria Azarenka.
The two finals are liable to be more competitive than the latest showdown in tennis' best rivalry, which produced a rare dud.
Federer's flop will fuel speculation he's losing ground to the game's best players at age 29. During his postmatch news conference, he bristled when asked if proving he's still a champion is a hassle.
"The bigger hassle is being asked all the time these questions," he said. "I don't know how many times I need to answer until I just say I'm not going to answer it anymore. But I know that I can do many more things in the game. I'm very excited by what's to come still. I don't feel like I'm 35 like you guys make me sound I am. I'm still only 29, and I have many more years left."
The first matchup in the United States in six years between Rafa and Roger generated plenty of buzz, with tickets shortly before the match fetching several hundred dollars. They met before a final round for the first time since 2007 because Federer recently slipped from second to third in the rankings and landed in Nadal's half of the draw.
The rankings had it right: Now the No. 1-ranked Nadal and No. 2 Djokovic will play for the championship. Nadal seeks his first Key Biscayne title, while Djokovic won the tournament in 2007.
"He's playing fantastic," Nadal said. "I just can congratulate him about what he did the first three months of the season. On Sunday I have to play very well all the match if I want to have any chance."
Federer is 0-4 this year against Nadal and Djokovic and 22-0 against everyone else.
"I wish I could play better right now against those guys, but it is what it is," he said. "I'm the last guy who gets pulled all the way down and then can't get up for the next tournament."
Against Nadal, Federer was in trouble early, committing four unforced errors to lose serve and fall behind 2-1. That was part of a stretch where Nadal won 13 of 15 points to take control. He lost only two of 18 points on his serve in the first set.
The chanting started after Federer fell behind 3-love in the second set. He said the crowd support was nice but added, "I'm not sure I wanted it or not, because it meant I was down in the score."
He had trouble coping with the velocity of Nadal's groundstrokes, shanking half a dozen shots, including one to reach match point. Then Federer put a tentative forehand in the net, and it was over after only 75 minutes.
Nadal never lost serve, converted four of five break-point chances and committed only 10 unforced errors to 31 for Federer.
Nadal has now won 15 of their 23 matches. He's 16-8 against Djokovic but lost when they met in the final at Indian Wells two weeks ago.
Even so, Djokovic is claiming the role of underdog Sunday.
"I obviously wouldn't feel like a favorite," he said. "For me to win, I will be have to be on the top of my game."
Fish, who earned the No. 1 American ranking thanks to his run this week, hung with Djokovic for a while but went 0 for 6 on break points. Djokovic erased three with aces and another with a service winner.
The Serb's serve was his biggest weakness only a year ago, but it's much-improved since. He has yet to be broken in 40 service games at Key Biscayne, erasing all 15 break points he has faced.
"I don't feel invincible," Djokovic said. "I don't feel that I can't lose on the court. What I feel is big confidence. What I feel is that I'm playing best tennis of my life."
Djokovic also is dominating long rallies, another reason he has lost only 18 games in five rounds.
"He's moving better than anyone right now, no doubt about it, on a hard court," Fish said. "It's his playground right now."
Based on reporting by The Associated Press.