KEY BISCAYNE, Fla. — As Andy Roddick offered a congratulatory handshake at the net to Nikolay Davydenko, the stoic Russian erupted in laughter.

Beating Roddick felt that good.

Roddick tried for an encore today, but Davydenko stole the show, winning 7-6 (5), 6-2 in the semifinals of the Sony Ericsson Open.

Roddick was coming off an emotional victory the night before, when he ended his streak of 11 consecutive losses to top-ranked Roger Federer. This time it was the No. 4-seeded Davydenko with the breakthrough — Roddick was 5-0 against him previously.

"That's probably the best he's played against me," said Roddick, who was philosophical about his roller-coaster 24 hours.

"I'll choose to leave here looking at the positive. I'm obviously disappointed tonight. But to have a win like I did over Roger was big for me, and hopefully that will stick with me a little bit more."

Davydenko's opponent in the final Sunday will be No. 2-seeded Rafael Nadal, who beat Tomas Berdych 7-6 (6), 6-2.

In the women's final Saturday, Serena Williams seeks her fifth Key Biscayne title and second in a row when she plays No. 4-seeded Jelena Jankovic.

"I've played a great tournament," Williams said. "I'm just happy to be still in it and doing the best I can do. As long as I'm doing the right thing on the court, I feel like I can come out on top, but I just have to make sure I'm doing what's right."

Roddick was forced into grinding rallies by Davydenko, who chased down shots all over the court and served well, facing only one break point. Standing 6 feet behind the baseline, the Russian began reading Roddick's booming serves in the tiebreaker, when he won the final four points served by Roddick.

In the second set Davydenko rallied from a break down to sweep the final five games, breaking Roddick three times in a row.

"If I come in a little bit to start to returning, I have no chance. It's too fast," Davydenko said. "It doesn't matter how you return — just in the court, and then you try your best."

Davydenko has been playing under a cloud because of an ATP investigation into heavy and odd wagering on an otherwise insignificant match he played in Poland last August. Davydenko says he did nothing wrong, and he has criticized the ATP for not reaching a resolution in the case.

"I feel good now," he said. "I forget really everything."

He's the first Russian man to reach the Key Biscayne final, and he's seeking his first tournament title this year. He said he's playing well because he changed rackets before the event, and has used the same racket in all five rounds.

"It has a little bit more string, and I have more control," he said.

The 5-foot-10 Davydenko lost only five points on his first serve. Typical of his serving dominance was the eighth game, when he fell behind love-15, then won the next four points with two service winners and two aces.

"The thing about him you normally don't see is the way he served tonight," Roddick said.

Davydenko was a little lucky, too. When his forehand skipped off the net cord for a winner and a 6-4 lead in the tiebreaker, Roddick flung his racket in dismay, and Davydenko patted the net in gratitude.

In the second set, Davydenko skipped another winner off the net cord to break for 2-all, then waved an apology with both hands toward a frustrated Roddick.

Afterward, what did Roddick tell Davydenko that made him laugh?

"He had no chance how to beat me," Davydenko said.

Nadal needed seven set points to close out a 73-minute first set against Berdych, then pulled away. Nadal committed no unforced errors in the second set, won 16 of 17 points on his serve and swept the final 12 points.

Nadal gleefully skipped at the net when he put away a volley to reach match point. He then hit a forehand winner and sank to his knees in jubilation.

"I am playing very well this tournament," Nadal said. "Today was a great match, too."

Nadal, the runner-up to Federer at Key Biscayne in 2005, is pleased to be back in the final but unhappy to still be in the United States. The tournament traditionally was held in mid-March but now stretches into April because of its television contract, and Nadal complained the change condenses the upcoming clay-court season.

"If you see the calendar, that is unbelievable," said Nadal, whose best surface is clay. "It's not fair."

The No. 10-seeded Berdych lost his serve for only the second time in the tournament to fall behind 5-3, but he dug in from there. Nadal had a set point in the ninth game, two more in the 10th and three in the tiebreaker before he closed out the set when Berdych double-faulted for the first time.

Berdych sagged in the 85-degree sunshine. He began to struggle with his dangerous forehand and finished with 34 unforced errors to 11 for Nadal.

"It was like my battery's gone," Berdych said. "If you are not 100 percent with him, then it's really tough to play."