SHANGHAI, China — Andy Murray will have an avid fan when he plays Roger Federer at the Masters Cup on Friday.

Nikolay Davydenko faces the winner in the semifinals, and he's dreading the prospect that it could be Federer — for good reason. He's 0-12 against the second-ranked Swiss star, and 3-3 against Murray.

"Against Murray, I have more chance," Davydenko said after beating Juan Martin del Potro 6-3, 6-2 today to reach the semifinals.

Federer, who lost his opening match to France's Gilles Simon, has to win to continue pursuit of his fifth Masters Cup title.

If Federer loses, Simon advances even if he loses to 26th-ranked Radek Stepanek, who replaced Andy Roddick when the American pulled out with a sprained ankle. Simon only got into the elite field because top-ranked Rafael Nadal withdrew before the tournament began.

Murray is in the semis no matter what, but vowed he won't try to take it easy to save energy. He would prefer to have Federer out of the competition. After all, the Swiss star lost his first match last year and still won the season-ending tournament, and Murray doesn't want to lose momentum.

Davydenko's defense and relentless groundstrokes were the difference against Del Potro, turning an expected tight match — the winner was guaranteed to go through — into a rout. He broke Del Potro's serve four times in eight chances.

"Today, I played so good," Davydenko said. "I feel great."

Earlier, Jo-Wilfried Tsonga of France beat Novak Djokovic of Serbia 1-6, 7-5, 6-1. Djokovic had already been assured of a spot in the semis. Tsonga had been eliminated.

Del Potro was unable to put much pressure on his Russian opponent in the first set, connecting on only 42 percent of his first serves.

Serving while trailing 4-3, Del Potro double-faulted to set up break point. Davydenko put away a forehand winner off a short ball for the game, then held at love for the set.

After Del Potro held to start the second set, Davydenko won five straight games, leaving the Argentine looking increasingly frustrated. Del Potro held to get to 5-2, but Davydenko finished it off by holding at love.

Del Potro wasn't sure what happened to him. He said he didn't see the ball well, was moving slowly and never found a rhythm.

He still was happy about his performance this year — rising rapidly to the top 10, putting together a 23-match winning streak and qualifying here — and looking forward to next week's Davis Cup final between Argentina and Spain.

"I'm living a dream," said Del Potro, whose early exit here will give him a couple of extra days to prepare to face a Spanish team that will be without Nadal.

Tsonga, who lost to Djokovic in this year's Australian Open final, looked listless before coming alive and winning five consecutive games from 5-5 in the second set to take control.

"He was better than me in the two first sets, but I take the second one," said Tsonga, who has beaten the third-ranked Serb the last three times they have played. "It was a holdup."

Tsonga was unusually subdued early in the match, showing only flashes of the form that carried him to the Paris Masters title — an event he had to win to qualify for the Masters Cup.

Djokovic, continuing his efforts to close in on Nadal and Federer at the top of the rankings, broke Tsonga twice while finishing the first set in only 25 minutes.

Tsonga pulled himself together in the second set and finally broke as Djokovic served while trailing 6-5. The Serb had four unforced errors in the game, sending a forehand long on set point.

Another four mistakes handed Tsonga an early break in the third set. Tsonga broke again, at love, to take a 5-1 lead, then held at love, flicking a lob winner on match point.

"In the third set especially, he played well," Djokovic said. "I made some unforced errors. The important thing is that I'm through."