Atlanta, Georgia, July 24: Andy Roddick had to battle a slow start before bludgeoning his way into the semi-finals of the Atlanta Tennis Championships Friday over the opponent he beat for the title in 2001.

The American rallied to defeat Belgian Xavier Malisse 4-6, 6-3, 6-4 in a re-run of the final nine years ago which marked the first career ATP title for a teenaged Roddick.

But Malisse, who turned 30 this week, made the American work for victory, claiming the first set on the back of a monster seventh game to break the top seed from Texas.

Roddick saved five break points and fired five aces before a back hand error handed over the game. Malisse carried the momentum to win the set but was broken for 2-4 in the second as Roddick regained equilibrium to claim his ninth victory in the decade-long series with Malisse.

It took just over two hours for Roddick to survive with 17 aces.

"Plan A wasn't working and the match was getting away from me," said Roddick. "I decided to make him work for the last nine or ten games.

"Nothing felt comfortable in the first set, but I tried to get aggressive, I wanted to grind back.

"He played well but he let me off the hook a bit. We were both gutting it out at the end."

The holder of 29 titles, including Brisbane and Miami this season, will play in the last four against sixth seed Mardy Fish who beat Taylor Dent 6-3, 6-0.

Wimbledon marathon man John Isner kept it short and sweet in 48 Celsius on-court heat, dismissing Michael Russell 6-1, 6-2.

Isner's win in 58 minutes was around 10 hours less than his Wimbledon epic of a month ago, when he won the longest match ever played in the sport.

The second seed, who admitted he was glad to get off court in a hurry, will play in semis against former university tennis opponent Kevin Anderson after the South African crushed Lukas Lacko 6-3, 6-4.

Isner said that after stuffing his racket bag in a closet for a fortnight following his second-round exit from Wimbledon, he came to Atlanta without much training.

"I felt better today than I did in my first match," said the graduate of the University of Georgia, quite at home with the local fans. "I knew that I would need to play better - even in this ridiculous heat."

The huge hitter fired a modest 11 aces against his fellow American on the way to his fourth semi-final of the season. His unforced-error count remained low at seven, with more than 20 winners.

While he's tired of talking about the Wimbledon match that secured his name in the record books, Isner said that he is glad it's all over and he can concentrate on the upcoming US Open starting August 30.

"I'm back to hardcourt, which is my favourite surface," said the 25-year-old ranked 19th. "I want to focus on doing well over the summer. I think that Wimbledon made me a batter player.

"But the bottom line is that I did lose in the second round there."

Isner stands 3-0 lifetime over the 32-year-old Russell, winner of a dozen lower-level Challenger titles.

Isner and Anderson have a history both in colllege and on the ATP.

"I remember I took him out when we played Illinois for the (university) championship," said Isner.

"He's playing well now. He has rolled through the tournament. He has a huge serve and forehand. It will be tough."