Wimbledon runner-up Andy Roddick withdrew yesterday from the US Davis Cup team's quarter-final at Croatia, citing a right hip flexor injury.

The US 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 towelled off.

The 26-year-old American would go on to play for more than another 90 minutes, 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 US 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 to 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," US captain Patrick McEnroe said.

Croatia host the US on clay at Porec, Croatia, starting Friday.