JOHNS CREEK — After losing a second-set tiebreaker, Andy Roddick needed some confidence.His two opponents, Rajeev Ram and the stifling Georgia heat, were bearing down.

"The first game of the third, I was down a couple of break points," Roddick said. "If he breaks the first game of the third, I think it's a long way back because he started serving a little bit better in the second set. That was probably the pivotal moment in the match."Roddick, the No. 1 seed, endured blistering temperatures to beat Ram 6-1, 6-7 (1), 6-3 in the second round of the Atlanta Tennis Championships on Thursday.

No. 3 seed Lleyton Hewitt of Australia lost the late match 4-6, 2-6 to Lukas Lacko of Slovakia.

Hewitt blamed an injury, which he refused to disclose, with keeping him from playing at full capacity. He acknowledged, however, that the injury occurred before he arrived in Atlanta.

"On Sunday, I didn't think I'd be able to compete here," Hewitt said. "For me, it was a good effort by the medical staff to be able to get me close to being 100 percent here."

Roddick, who will face seventh-seed Xavier Malisse of Belgium in the quarterfinals, is aiming for his 20th career tournament title on hardcourts and third this year.

Malisse defeated Ukraine's Illya Marchenko 6-3, 6-3.

Roddick, the world's ninth-ranked player and highest-ranking American, improved his ATP tour-leading match record to 27-4 on hardcourts.

Late-afternoon temperatures ranged in the mid-90s with a heat index of 100 at the Atlanta Athletic Club.

Roddick, who hadn't played a singles match since falling in the fourth round at Wimbledon last month, blamed the heat for causing his left foot to swell.

During the third set, he nearly asked for a trainer before reconsidering.

"I don't know if it's a bruise or a nerve," Roddick said. "I was going to get it worked on and treated, but I wasn't sure how it would react. It felt swollen, so I was a little scared of taking the shoe off and having it blow up a little bit. It's something that I've had before. It's manageable. It's something that happens if you haven't been in the heat for a while."

Roddick's first career victory came against Malisse in 2001 at the same venue. That was the last time the Atlanta championships were held before the event returned this year.

Improving to 33-7 this year, Roddick showed some frustration by throwing his racket in the second set, but he finished the match having won seven of eight break points, including a 4 for 4 on service saves.

Roddick had not lost a 7-1 tiebreaker since dropping a first-round match to Gilles Muller at the 2005 U.S. Open. It marked just the fourth time in his career that Roddick lost a 7-1 tiebreaker or worse.

"There's basically two ways to look at a tiebreaker," Roddick said. "You lose one or you win one. It's the same with a match. You lose or you win. It doesn't matter how many games you win. If that was the case, I probably would've won Wimbledon last year."

No. 6 seed Mardy Fish withdrew from doubles Thursday after twisting an ankle late in a second-round singles victory the night before over Robby Ginepri.

Fish, who needs to rest before his quarterfinals match, was supposed to team with Roddick in the postponed doubles match.

In quarterfinal singles, Lacko will play Russia's Kevin Anderson, a 7-5, 6-3 second-round winner over Donald Young. After No. 2 seed John Isner faces Michael Russell, Roddick-Malisse and Fish-Taylor Dent are the night matches.

Hewitt, ranked No. 30 in the world, double-faulted seven times and succeeded on just 38 percent of first serves.

"I just didn't have quite a lot of rhythm out there," Hewitt said. "Pushing off on my serve wasn't the best. I was just putting a lot of pressure on my service game."

Lacko could tell something seemed wrong with Hewitt, who underwent hip surgery in January and missed much of 2008 with a hip injury.

"Obviously, he's got some problems," Lacko said. "He was fighting through the first set. I played good ending to the first set and after breaking the second, he seemed like ... he had some minor problems. I mean he needed a couple of extra steps on his strokes."

Roddick doesn't foresee problems with his foot, though he planned to have treatment before bed and again on Friday.

If he hadn't played well in the third set, Roddick believes his foot would've hurt much worse.

"I started sticking my returns a little bit more," he said. "I missed a couple more in the third set, but the ones I made either were winners or were a little more aggressive. It was a little bit more on my terms, and I think what probably switched the match around for me."