The eighth-seeded Swede, who upset top-seeded Andy Roddick to reach the semifinals, lost to Michael Llodra in a third-set tiebreak last week in Rotterdam. Soderling will play Steve Darcis, who advanced to his second career ATP final by defeating Jonas Bjorkman 4-6, 6-1, 6-4.
Soderling did not play a match after July last year because of a left wrist injury, and now he's in his seventh career ATP final and second in Memphis. He improved to 3-1 against Stepanek, the No. 4 seed from the Czech Republic.
The Swede who spent his layoff practicing his serve and forehand three to four hours a day hasn't been broken this week or in his past 35 service games. He had 12 aces against Stepanek in winning 35 of 39 points on his first serve.
"I feel really good," Soderling said. "I think I played pretty good today even though it was a difficult match ... It's always difficult to play against Radek. I've played him four times now. It's tough. ... He's trying to make you play bad actually."
Stepanek, who lost to Roddick in the final at San Jose last week, missed a prime chance to break Soderling in the third game of the first set. But Soderling held, and they went to a tiebreaker where Soderling blew it open by winning the first five points with a couple of aces.
The turning point came with Soderling up 2-0 and Stepanek serving. An official called a fault, and Stepanek talked to chair umpire Blaze Trifunovski who answered, "I saw it was out." Stepanek said, "That means you didn't see it" before hitting wide to lose the next point.
In the second set, Stepanek had a chance to break Soderling again in the third game only to hit a return long. Soderling served up an ace, and Stepanek put a forehand into the net. Soderling then broke Stepanek to go up 3-2 and served out for the win. Stepanek tried to fight off match point in the ninth game with a drop shot called out, then he hit a forehand wide.
"I missed a return by 5, 10 centimeters. That's what tennis is about, using your chances," Stepanek said. "That's what I didn't do today.
Darcis, ranked 81st, is making his Memphis debut.
"It's a great moment," Darcis said. "I will try to have fun tomorrow. It doesn't matter who I'm going to play. Anyway it will be a tough match. I'll try to take the chance at what the other guy leaves me and see."
Darcis had won only two ATP-level matches this year. He reached the second round in Sydney and beat Lukas Dlouhy in Davis Cup play. He won his first title at Amersfoot in the Netherlands in July
Bjorkman played in the semifinals of the event for the first time since 1997 when he lost to Todd Woodbridge in the finals. He hadn't been in a semifinal since Nottingham last year and came in with 6-9 record in singles.
The Swede, who turns 36 later this month, defeated Paul Capdeville, No. 5 seed Sam Querrey and Donald Young to advance. He started off the semifinal looking as if he might continue his unexpected run, breaking Darcis in the third game of the first set and holding serve to win 6-4.
Darcis took control during the fourth game of the second set, which featured 18 points and four break points. Darcis broke Bjorkman to go up 3-1 as the Swede hit a forehand long and then put a backhand into the net.
"Unfortunately, I came up short against somebody who played a little bit better," Bjorkman said.
Bjorkman, who fought off eight of 11 break points, tried to answer in the third set and was serving well until the seventh game when Darcis broke the Swede to trail 4-3. Darcis served out the match and won as Bjorkman put another shot into the net.