World number one Roger Federer [Images] rolled into the semi-finals of the Cincinnati Masters on Friday while fourth seed Marat Safin [Images] was dumped out by American wildcard Robby Ginepri.

Fifth seed Andy Roddick [Images] battled past Russian Mikhail Youznhy 2-6, 6-3, 6-4 and now plays either third seed Lleyton Hewitt [Images] of Australia [Images] or sixth-seeded Russian Nikolay Davydenko [Images].

Top seed Federer let slip an early lead in the first set when his Argentine opponent Jose Acasuso recovered from 3-0 down to 3-3.

But once the Swiss, in his first event since he won a third consecutive Wimbledon [Images] title, had taken the first set it was plain sailing as he clinched a 6-4, 6-3 victory.

"I have the feeling I'm back," Federer said.

"My confidence is back. You lose it when you don't play, and you've got to earn it again. I am really happy with the way I'm playing now."

Federer will meet Ginepri in the last four after Safin, who had impressed in his victory over Dominik Hrbaty in the previous round, was dumped out 6-2, 6-3 in 56 minutes.

With Ginepri cutting down on the unforced errors, Safin self-destructed, smashing a ball out of the stadium and throwing his racket in disgust at his performance

"I just tried to stick to my game, that's what I've been doing all week," said Ginepri, who won the title in Indianapolis earlier this summer.

"This is definitely the best I've been playing and all the hard work I've been doing is paying off."

Safin, who is still struggling with a left knee injury, said he had half-expected a bad performance.

"I woke up this morning and didn't have any energy," he said.

"I couldn't really run enough and it's a little bit to be expected as I couldn't practise for a month and a half.

"I am now going to take a week off, not play New Haven [where he had been given a wildcard], and get ready for the US Open [Images].

"It's probably not enough matches, but it could have been worse. I beat some good players and could have lost first round here and first round in New Haven."

Roddick had not lost his service on the way to the last eight, but he was broken twice as Youzhny stormed through the first set.

But the former US Open champion became more aggressive and that paid dividends as he levelled the match and then broke in the fifth game of the decider on the way to victory.

"I think it started getting better when I began to serve better," Roddick said.

"The crowd helped me the other night against [Juan Carlos] Ferrero and they helped me again tonight."

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