WIMBLEDON, England — Wimbledon runner-up Andy Roddick withdrew Monday from the U.S. Davis Cup team's quarterfinal at Croatia, citing a right hip flexor injury.

The U.S. Tennis Association announced that Roddick wouldn't participate in this week's Davis Cup matches because he was hurt during his loss a day earlier to Roger Federer at the All England Club — a match that finished 16-14 in the longest fifth set in Grand Slam final history.

Roddick slipped and tumbled to the grass in the eighth game of the fourth set Sunday. He stayed down for a few moments, then rose, grimacing, and toweled off.

The 26-year-old American would go on to play for more than another 1<0x00BD> hours, finally succumbing when Federer broke him for the first time all match in the 77th and last game.

After the match, Roddick was asked whether he hurt himself in that fall, and he replied, "No. It was OK."

He is being replaced on the U.S. Davis Cup team by Mardy Fish, who reached the third round at Wimbledon. Roddick is ranked No. 6, while Fish is No. 23.

When he was asked to play Davis Cup, Fish pulled out of this week's Hall of Fame Tennis Championships in Newport, R.I., where he was the tournament's top-seeded player.

Roddick had played in 18 consecutive Davis Cup matches for the United States, helping the country with the 2007 title.

"Andy has been a stalwart for this team the past nine years, and his dedication to Davis Cup and his teammates is unquestioned," U.S. captain Patrick McEnroe said.

Croatia hosts the U.S. on clay at Porec, Croatia, starting Friday.

"Mardy is a Davis Cup veteran and we appreciate his willingness to join the team on short notice. He has been playing well and we are glad to have him back in the singles lineup," McEnroe said. "Andy had a great run at Wimbledon. He battled for more than four hours yesterday and fought hard to reach the final. Understandably, his body is not up for the rigors of Davis Cup in such a short turnaround."

Fish will be joined in singles action for the U.S. by James Blake, while twins Bob and Mike Bryan will play doubles.

Wimbledon quarterfinalist Ivo Karlovic and Marin Cilic will lead Croatia, which won the Davis Cup in 2005.

"It's worse for us," Goran Prpic, Croatia's Davis Cup captain, said in Porec. "Instead of an injured Roddick, who after such a final at Wimbledon would have had to play matches on clay, we'll have to face a motivated Fish."

Associated Press Writer Snjezana Vukic in Zagreb, Croatia, contributed to this report.