Tennis/ Masters Cup: World number one Roger Federer got his quest for a fourth Masters Cup title back on track with a 6-4, 6-3 win over Russian Nikolay Davydenko yesterday.

Following Federer on court, American Andy Roddick became the first player to book a semi-final spot at the season-ending event in Shanghai after crushing Chile's Fernando Gonzalez 6-1, 6-4.

Federer, stunned by Gonzalez in his Red Group opener on Monday, was again below his best but he was still good enough to eliminate Davydenko from the showcase eight-man tournament.

"It was a different situation coming back from losing," shrugged the Swiss, who had never lost a round-robin match at the Masters Cup before being ambushed by Gonzalez.

"Here you lose and you play another top-10 guy. This was a top-four guy, so it doesn't get any easier. Anything can happen in the men's game.

"You're a little bit off, you're a little bit tired, you'll lose right away. But I create myself many, many opportunities so eventually I'll break through and I'll break their will."

Federer, who owns a 14-1 record against Roddick, must now beat the American in his final group match tomorrow to avoid an early exit from the €3 million event.

With cow bells echoing around Qi Zhong stadium, Federer struggled at first to impose himself on Davydenko, an opponent he had beaten in all their previous 10 meetings.

Federer, who is bidding to win a fourth title in the last five years at the tournament, did just enough to take a scrappy first set despite 22 unforced errors.

He broke to lead 5-3, promptly dropped his serve but restored normal operations in the next game, breaking again to win the set when Davydenko blew an easy smash.

Federer raised his game in the second, a forehand rocket giving him a 3-1 lead, and he quickly put Davydenko out of his misery to kick-start his title challenge.

Davydenko, who will be involved in the Davis Cup final starting later this month, already has his getaway planned once his Masters Cup commitments are over with. "I fly to the Maldives on Sunday for one week for a rest," said Davydenko.

Gonzalez suffered a letdown after his upset over Federer, Roddick steam-rolling the Chilean in just 65 minutes to reach the semi-finals for the third time in four appearances.

"Some days you have good days where everything feels pretty clean," said Roddick, who will play for the US in the Davis Cup final in Portland, Oregon. "This was one of those."