French Open runner-up Söderling is fighting for one of two remaining spots in next month’s eight-man ATP World Finals in London, standing provisional ninth behind Nikolay Davydenko and Fernando Verdasco.
The Swede, who was runner-up to Argentina’s David Nalbandian in 2008, shook off an early break before taking victory in 1 hour and 43 minutes.
He can gain some ground this week, though not pass Verdasco, who will not play until Valencia in ten days’ time.
Söderling now faces 2006 Australian Open finalist Marcos Baghdatis in the semis after he eliminated Frenchman Arnaud Clement 6-4, 6-4.
Tenth-ranked Söderling was playing in the tenth quarter-final of his breakthrough season, improving to 45-18.
Meanwhile, Brazil’s Thomaz Bellucci fired 18 aces to defeat Joachim Johansson 7-6 (7/4), 6-3 in their quarter-final to leave Soderling the last home hope.
Bellucci, 21, whose last quarter-final appearance in August led to a career breakthrough trophy on clay at Gstaad, will play on Saturday for a spot in the final against Oliver Rochus after the Belgian defeated Finn Jarkko Nieminen 6-3, 2-6, 6-1.
The ace output of Bellucci, ranked 45th, was almost matched by Johansson, who fired 13.
The Brazilian winner saved the lone break point he faced while Johansson lost his own serve once.
“I stayed concentrated throughout the whole match. I served very well which took pressure off me, so I was very happy with that,” said the South American.
Johansson’s lack of consistent match play due to years of shoulder injuries showed as he went down to defeat in his fourth Stockholm quarter-final.
The 27-year-old Swede’s best performance here was a run to the 2006 semi-finals, when he lost to Nieminen, also currently coming back from injury after spring wrist surgery.
Johansson stands 12-8 indoors at home and was playing his first quarter-final since January, 2007, in Adelaide, where he lost to Novak Djokovic.
“He’s trying to come back and he’s playing very well,” said Bellucci. “If he keeps playing like that, I’m sure he’ll be back very soon.”