If not for the scoreboard, no one seated in the Grandstand court yesterday afternoon would have guessed that Brian Baker was about to upset the ninth seed at the U.S. Open.

It was a humid first day of tennis, and the 20-year-old American looked like he had run from Manhattan to Flushing. Sweat poured from beneath his baseball cap; his shirt was soaked. When his opponent, 2004 French Open champion Gaston Gaudio, would hit a soft backhand drop shot, Baker would not even give chase.

Yet there was Baker in the third set, up two sets to none and a break of serve. After stopping to receive treatment for a cramp in his left leg, he tentatively served his way to a 5-3 lead in the set. Two games later, he served out the match, securing his first ever victory in a Grand Slam event, 7-6 (9), 6-2, 6-4.

For Baker, a native of Nashville, Tenn., the victory was a high point in a season of struggles. A wrist injury sidelined him from the middle of February until early May. He reached the final of his first tournament, a second-tier event in Mississippi (he lost to James Blake), but then injured his knee while attempting to qualify for Wimbledon.

While he said he expected to have a chance against Gaudio, a clay-court specialist, he knew he would have to serve well and dictate play to come out on top.

“If you’re top 10 in the world, it’s not like you are going to be a slosh on a hard court,” Baker said. “I knew I’d have to come out there and play my best tennis, and fortunately, I did.”

While Baker looked exhausted on the court, Gaudio seemed as fresh as could be. Yet he seemed to play with indifference. When Baker hit a near impossible passing shot, Gaudio smiled. He joked with the chair umpire when Baker called for the trainer, clearly confused by the fact that the man who was whipping him needed help.

Only in the first set, after he failed to break for a 5-4 lead, did Gaudio show some emotion, smashing his racket on the ground and cracking the frame. He saved three set points in the tiebreak and earned one of his own before he sliced a return long.

Baker’s serve sealed the match. After letting a Gaudio forehand drop into the corner without taking a swing at it, Baker fired an ace and two service winners for a 40-15 lead. Overall, he won 75% of points on his first serve and 61% on his second. Gaudio broke him just one time.

Afterward, Baker said he did not mind that it took him three tries at the U.S. Open before he won a round. Once a top-ranked junior with a blistering two-handed backhand, Baker decided to turn pro rather than attend a top tennis college like Stanford or the University of Florida. He said he still hopes to become a top 10 player – he is now ranked 172nd – and win a Grand Slam title.

“I would have loved to have done a little bit better, but I’m still happy where I am,” he said. “And with hard work, I hope I can get up there.”