U.S. captain Patrick McEnroe made Roddick the No. 1 player Thursday for the quarterfinal match with Spain. Several days of treatment helped Roddick recover.
"It feels all right," Roddick said of his left hamstring. "I'm going to play and I'm excited about it."
He'll face Fernando Verdasco, chosen as Spain's No. 2 player ahead of David Ferrer, in today's second singles match. James Blake will face Tommy Robredo in the first match today on the indoor hard court.
Saturday's doubles match pits top-ranked Mike and Bob Bryan against left-handers Verdasco and Feliciano Lopez. The reverse singles matches in the best-of-five event are Sunday.
While Roddick will play through his injury sustained at the Sony Ericsson Open, Spain will be short-handed. Rafael Nadal, No. 2 in the ATP rankings, is home, citing a sore foot. He may also be interested in preparing for the clay-court season.
Spain reached the quarterfinals in part because No. 1 Roger Federer sat out Spain's 3-2 win over Switzerland in the first round.
Nadal and Federer aren't the only who have shied away from the Davis Cup. Jimmy Connors competed in only 13 singles matches.
Roddick is motivated to end the record 12-year Davis Cup title drought for the U.S.
"First of all, we haven't won it. I think that's a big thing for all of us," Roddick said. "It is one of sport's ultimate honors, to be asked to represent your country."
Roddick is 22-9 in Davis Cup singles matches since his 2001 debut. Roddick won both of his matches, including the clincher against Tomas Berdych, in the 4-1 first-round win over the Czech Republic in February.
McEnroe appreciates Roddick's and Blake's dedication to the Davis Cup.
"Just the fact that all the guys have always been there every single time they've been asked, I think people respect that, and it inspires people to want to be part of it," McEnroe said.
Roddick will be key for the Americans' chances. He's 7-0 against Robredo, without dropping a set, and 5-2 against Verdasco.
The only surprise from Thursday's draw was Spanish captain Emilio Sanchez's decision to go with the 35th-ranked Verdasco ahead of No. 16 Ferrer as Spain's No. 2 singles player.
"I had difficulty choosing who was going to play, but Fernando had a very good week of practice and adjusted well to the surface," Sanchez said. "So I hope that he has a competitive match."
It's a rematch of the 2004 final, when the U.S. lost at Spain on a slow indoor clay court. Spain isn't favored this time because of Nadal's injury, the surface and the sellout crowds of more than 14,000 expected each day.
"With Andy, it will be tough for sure," Verdasco said. "But I think I've had good preparation. We have nothing to lose."
Blake is more of a concern for the Americans. After an impressive start to the season, which included winning a tournament in Sydney and a fourth-round appearance at the Australian Open, Blake has struggled. He's dropped six of his past nine matches and has fallen four places to No. 9 in the rankings.
"If this was four or five years ago, I would have had a tougher time standing up here and saying I'm confident," Blake said. "But being a little older and hopefully a little more mature, I realize there are going to be ups and downs in everyone's career. I've had a good week of practice."
The U.S. will be big favorites in Saturday's doubles. The Bryan brothers are 10-1 in Davis Cup matches.
The U.S.-Spain winner will face either Sweden or Argentina in the semifinals Sept. 21-23.