Stockholm  - German Tommy Haas tested his recent Shanghai shoulder niggle with resounding success Wednesday, opening his account at the Stockholm Open with 17 aces on the way to a 6-3, 6-4 defeat of Frenchman Florent Serra.

The 31-year-old Haas showed no sign of the fitness concerns which forced him to hand over a second-round win in China to compatriot Rainer Schuettler after just one set.

The second seed in the Swedish capital took just 55 minutes and never faced a break point in his hammering of number 68 Serra to earn a 2-0 record in that series.

"It's holding up," Haas said of his shoulder, which has undergone multiple surgeries over the years. "There were a lot of nice quick points today, that suited me well.

"I served extremely well. I'm happy with how I played, but there's still room for improvement of course."

Haas has two previous semi-finals at the Kungligahallen from 2004 and two years ago. His first loss in the final four came against Andre Agassi while he went out to eventual 2007 champion Ivo Karlovic.

The German with a Halle title on grass so far this season said that he's watching his back at an event where he next plays Finn Jarkko Nieminen for a quarter-final spot.

"Everybody knows that men's tennis is getting tougher and tougher - everybody's dangerous out there," said the 31-16 Haas. "I have to look round by round, like I do at every tournament.

"There are a lot of players that are hungry to do well at the end of the season."

Spain's veteran Feliciano Lopez, the number eight, followed the Haas winning example.

Lopez beat Ernests Gulbis of Latvia 6-2, 6-4 four days after failing to finish due to foot and ankle pain in the Shanghai semi-finals against Rafael Nadal, his best result of a disappointing 2009 campaign.

But a flight halfway across the world back to Europe did wonders for his fitness, with the left-hander who loves a hard-court streaming through in 53 minutes with eight aces and four breaks of serve.

Gulbis, loser of ten previous first-round matches this season, made a minor breakthrough this month with a Tokyo quarter-final against Jo-Wilfried Tsonga, but has slipped back to his previous form with the defeat by Lopez in their first meeting.

Top seed Robin Soderling, still in the chase for one of two remaining spots for next month's ATP season-ending championships, will make his first start since breaching the Top 10 for the first time on Monday.

The French Open finalist faces a first-round match with lucky Loser Giovanni Lapentti of Ecuador.

Soderling became the 17th Swede in the history of the rankings (since 1973 with Bjorn Borg) to appear in the Top 10. The last local to do it was Jonas Svensson in 1991.(dpa)