Saturday, 21 July 2012:

Australian Matthew Ebden had no answer to Gilles Muller's dominant serve as he lost his quarter-final to the Luxembourger in straight sets at the ATP's Atlanta Open on Friday.

Muller didn't face a break point as he won 32 of his 35 first-serve points and broke Ebden once in each set to win 6-4 6-4 and set up a semi-final against Japan's Go Soeda.

Perth-based Ebden struck 20 aces in his previous round against James Blake, but was this time on the receiving end as world No.63 Muller took just 72 minutes to wrap up the match.

Muller is bidding to win his first ATP Tour title, with his last final appearance coming in Los Angeles nearly seven years ago.

Soeda upset Olympics doubles partner Kei Nishikori 6-2 6-1 to advance in the first match-up of two players from Japan in an ATP quarter-final since the Open era began in 1968.

The other semi-final will be between top seed John Isner and veteran Andy Roddick in a heavyweight all-American clash.

Isner won a hard-fought tiebreaker in the first set and held off teenager Jack Sock 7-6 (9-7) 6-4 in a match delayed by a one-hour rain delay.

"I came out flat after the rain delay," Isner said.

"Had it not rained, I could have won the first set a little more easily. That took a little out of me."

Roddick had earlier progressed to the final four with a comfortable 6-3 6-4 win over Michael Russell.

Roddick won 86 per cent of his first serves and faced only one break point. He had 12 aces.

"If I could take the serving stats from today and apply them to any match, I would sign up right now," Roddick said.

AAP