WASHINGTON — After fourteen points in the third-set tiebreaker and 2½ hours of tennis, Andy Roddick and Juan Martin del Potro stood at the net, waiting for the scoreboard to tell them if they would continue to play.

Del Potro had apparently won the match with a crosscourt forehand winner, but after Roddick challenged the call, both players expected play to continue.

"I actually thought it might have been out, and I asked him and he said it might have been out," Roddick said. "So imagine the disappointment when it wasn't."

The replay system confirmed the ball hit the outer portion of the sideline, giving del Potro a 3-6, 7-5, 7-6 (6) win and his second straight Legg Mason Tennis Classic title. Del Potro raised both arms above his head in celebration before embracing Roddick across the net.

It was the first loss for the top-seeded Roddick in four Washington finals. Roddick won the tournament in 2001, 2005 and 2007.

Roddick began this tournament with some uncertainty about his game. He hadn't played in a match since losing an epic Wimbledon final to Roger Federer on July 5 and taking a monthlong break to recover from a right hip flexor he injured in that match.

Roddick said he feels good about how he played in Washington, a hard-court tournament that is a warmup for the U.S. Open, which begins August 31.

"Coming in here after being off for a month, you want to find out where your form's at, you want to get a bunch of matches in," Roddick said. "I feel I'm on the right path toward the Open."

The long match under a hot sun took its toll on del Potro. The second-seeded Argentine acknowledged after his semifinal Saturday afternoon the heat wore him down and the weather was even warmer Sunday, with temperatures in the mid-90s.

"It was so difficult for me," del Potro said. "After the first set I couldn't move anymore."

Roddick had largely avoided the sun in the tournament by playing all night games prior to the final.

"I think he might have been feeling it more than I did," Roddick said. "He didn't want to get into long points and was kind of going for broke there. He was kind of rolling the dice, and he hit Yahtzee a bunch of times."

Del Potro double-faulted on all three break points he faced — one in each set — but he had no problems serving at the end.

"It's bad for your mind," del Potro said. "I did many double-faults, but I always was thinking to keep trying to the final, and if I did good returns, maybe I'll have the chance to break his serve, and I did.

"We play until the tiebreaker, and then I did the best service of my life."

Del Potro had five of his 19 aces in the tiebreaker, including one on a second serve. That was the only time he missed on his first serve in eight chances during the tiebreaker.

Del Potro lost serve for the third time in the match in the third game of the final set. With the score 30-all, he attempted to smash a high lob and missed, hitting it long. On the ensuing break point, he double-faulted and gave Roddick a 2-1 lead.

Roddick gave the advantage back with his own double-fault on break point to even the set 3-all. Roddick's service loss was part of a run of 11 consecutive points won by del Potro.

That was the last break either player faced, with both holding serve until the tiebreaker.

Although there were some key errors for both players, most shots worked. Roddick had 20 unforced errors and 44 winners, while del Potro had 32 errors while hitting 50 winners.

"I kind of forced him to play high-risk tennis, especially with the heat," Roddick said. "He was taking big cuts, especially for the last 30, 45 minutes we were out there, and he was connecting."