JOHNS CREEK — No. 1 seed Andy Roddick beat Xavier Malisse 4-6, 6-3, 6-4 in the quarterfinals of the Atlanta Tennis Championships on Friday night.

Roddick pumped his fist and shouted in celebration after breaking serve in the ninth game of the third set. He said he used a new tactic in the service breaker, standing about 8 feet behind on the baseline on first return.

Before improving to 9-0 on the ATP tour against Malisse, Roddick struggled in the first set with two double-faults and had problems throughout the match in earning just six of 38 first-return points.

But Roddick, the tour leader this year with a 28-4 record on hard courts, never lost the power of his serve and finished with 17 aces. The capacity crowd at the Atlanta Athletic Club's stadium court was decidedly in his favor.

John Isner, the second seed, took less than an hour in the afternoon to beat Michael Russell 6-1, 6-2.

Isner, who rose to tennis fame with a record-long match at Wimbledon, showed why he's one of the ATP tour's service leaders with 11 aces and an 89 percentage on first serves.

He will face South Africa's Kevin Anderson, a 6-3, 6-4 winner over Lukas Lacko of Slovakia, in the semifinals.

Roddick will play Mardy Fish or Taylor Dent.

Club officials said the surface of the stadium court was 102 degrees during Isner's match, but the crowd favorite moved his feet more swiftly than he showed in a second-round victory Wednesday over left-hander Gilles Muller that lasted more than 2 1/2 hours.

"I remember just standing out there, not that I was feeling tired, it's just that sun is so intense," Isner said. "It's brutal when you're out there and you can't get a break from the sun, you can't get a breeze out there, so it's really tough."

Isner's record five-set match at Wimbledon took three days and over 11 hours to complete. He breezed past Russell in 56 minutes.

Despite the oppressive heat Friday, Isner could see the ball more easily than he did against Muller, allowing him to keep up a steady rhythm on his returns.

"I remember a couple of times the other night, he'd hit a shot, and I'd overrun it sometimes and I'd under-run other times," Isner said. "So the timing of my footwork was a lot better."

The 6-foot-9 Isner was cheered avidly throughout the afternoon by Georgia fans who remember his leading role in the Bulldogs' 2007 national team title.

Georgia's career leader in singles and doubles wins beat Anderson that year in a final-day match that helped the Bulldogs defeat Illinois before a raucous capacity crowd in Athens.

"I am so thrilled to have a tournament back in the South and especially in Atlanta," Isner said. "A lot of Bulldog fans reside in Atlanta, so it's good to have them on my side."

Isner, who went 3-0 against Anderson in college, is 2-1 in professional matches, including a straight-sets, second-round victory on hardcourts four months ago at Indian Wells, Calif.

"I'm going to have focus foremost on my serve," Isner said. "I think that's what he's going to do, too. If it comes down to tiebreakers, so be it. If I take care of my serve, I should have a good chance to maybe win."

Isner is the second-highest ranking American, 19th in the world, behind No. 9 Roddick, who won his first ATP title nine years ago against Malisse at the suburban Atlanta club.