Söderling will now face Japanese teenager Kei Nishikori for a place in the final after defeating the German number five Rainer Schuettler 6-2, 7-5.
Nishikori dismissed his own illness worries to advance into the semi-finals without firing a shot on Friday while top seed David Nalbandian was barely tested with a quick victory in just over an hour.
Nishikori moved through when his scheduled opponent Mario Ancic, the second seed, withdrew with fever before their match as ill-health continues to compromise the Croatian’s career.
Top-seeded Nalbandian earned his third ATP victory over Spain’s Albert Montanes 6-1, 6-4 with minimal effort to set up a semi-final with Finn Jarkko Nieminen.
“I played well, really well,” said the Argentinian. “It will be a tough match against Jarkko. He’s a lefty but if I play like I have this week I have a good chances.”
Nieminen, who polished his tennis in Stockholm early in his career, continued his quest to try to go one better after losing two finals with a 6-1, 6-4 win over Spaniard Oscar Hernandez.
Nishikori said that he had considered retiring himself before the match after carrying a cold, sore throat and knee pain all week.
“But I didn’t, I just wanted to play the match,” he said. “I’m sick too. But I’m in the semi-finals, that’s big.”
Ancic, who missed six months of play in 2007 with a serious case of glandular fever and was out for much the summer with a relapse, was unable to take to the court.
The Croatian was struck down by fever and bronchitis to hand the 18-year-old Nishikori a first semi-final since Delray Beach in Florida last February.
Nishikori, ranked 77th, is fast-tracking up the ATP rankings and is the first serious contender from his country since Top 50 Shuzo Matsuoka a decade and a half ago.
Nishikori, who has lived for the past four years at the Nick Bollettieri academy in Florida, won his first career title in Delray as he beat number 12 James Blake in the final.
Nalbandian easily dominated Montanes, the number 46 who won a clay title in Amsterdam this season, breaking once in the first set and twice in the second.
The Argentine is focussing his season on the Davis Cup final against Spain from November 21-23 in Mar del Plata.
Nieminen, the losing Stockholm finalist in 2001 and 2006, broke Hernandez five times in just under 90 minutes on his way to victory.
The 27-year-old currently stands 33rd, down from a career-best ranking of 13th in the summer of 2006.