ESPN Tennis

SHANGHAI, China -- Andre Agassi and Rafael Nadal withdrew from the Tennis Masters Cup on Monday because of injuries, leaving Roger Federer the only top-five player in the elite field.

And even Federer, the two-time defending champion, might not go the distance. The top-ranked Swiss has a sore ankle.

The $4.45 million season-ending tournament is supposed to assemble the world's eight best players, but injuries and absentees have removed some of the gloss.

Agassi lost 6-4, 6-2 to Nikolay Davydenko and then pulled out after aggravating an injury to his left ankle.

"With the state of my ankle right now, there's no chance for me to be able to play again," Agassi said. "It's very dangerous and risky for my future to be ready for anything in the next four or five weeks."

Nadal, ranked No. 2, withdrew while Agassi was on court. The 19-year-old Spaniard was supposed to play Gaston Gaudio in his opening match in his group.

Nadal said doctors advised him not to risk further damage to ligaments in his left foot. The French Open champion hurt himself during a victory over Ivan Ljubicic last month in Madrid.

Mariano Puerta replaced Nadal, becoming the fourth Argentine in the field. On short notice, Puerta lost 6-3, 7-5 to Gaudio. Fernando Gonzalez of Chile will take Agassi's place in two remaining round-robin matches in the depleted Gold Group.

"Having both Raf and Andre injured in one day is extraordinary," tournament director Brad Drewett said. "And it comes on the back of three other significant withdrawals."

Pulling out before the tournament were third-ranked Andy Roddick (back) and Australian Open winner Marat Safin (knee). Lleyton Hewitt, ranked fourth, remained in Sydney with his wife, actress Rebecca Cartwright, who is expecting the couple's first child within two weeks.

"It's unprecedented and unfortunate to have this number of players injured at the same time," Drewett said. "No doubt, we still have good players, starting with Roger."

Agassi said the surface of the hardcourt at Qi Zhong Stadium contributed to his decision.

"It's very sticky. It stops and everything else moves. It's hard to have confidence. Then when you try a little bit, it's still painful," he said. "Today was obviously taking a chance to test [the ankle] out. I was just getting worse. It's not ready."

Federer beat Argentina's David Nalbandian in his opening match Sunday and leads the Red Group. On Tuesday, he plays Croatia's Ivan Ljubcic, who defeated Argentina's Guillermo Coria.

Nadal said he hadn't been able to play or train properly for three weeks.

"I had a lot of inflammation in the foot after Madrid," Nadal said. "After I came here, I had more pain."

Agassi was playing in his first tournament since losing the U.S. Open final to Federer in September.

"When you haven't played in so long -- I couldn't really hit balls for a couple of months because of my sprained ankle -- you come back, try to get ready in a hurry and you force it," Agassi said. "And things just don't respond."

His latest loss extended his rough run in Shanghai to 0-4, including two matches at the 2002 Tennis Masters Cup before he withdrew and a first-round loss at a tournament in 2001.

Federer is recovering from an injury to his right ankle that has sidelined him for six weeks since he ensured the No. 1 year-end ranking with his 11th title of the season. He is 78-3 this season and was recognized as the winner of the 2005 ATP Champions Race before play Monday.

"I haven't lost my No. 1 ranking this year," he said. "So I will try to keep it up and who knows, I could be standing here in 365 days' time."

Copyright 2005 by The Associated Press