(CNN) -- Former world No. 3 David Nalbandian has continued his latest comeback from injury by reaching his first semifinal of 2010 at the Legg Mason Classic in Washington, but top seed Tomas Berdych suffered a shock defeat.
The Argentine is now ranked a lowly 117th after missing both the French Open and Wimbledon due to a hamstring problem, but proved too strong for Andy Roddick's conqueror Gilles Simon on Friday.
The 28-year-old, playing his first tournament since April, came from behind to beat the French 13th seed 3-6 6-2 6-3 and set up a clash with Croatian No. 4 Marin Cilic.
"I feel good. I will just try to keep believing in my game and play the best I can," Nalbandian, who missed most of 2009 due to hip surgery, told reporters.
"During practice I know I can go far. Without playing matches, it's tough to know how far you can go."
Nalbandian, four times a semifinalist in Grand Slams and the Wimbledon runner-up in 2002, made a poor start as he trailed 3-0 in the opening set and was then a break and 0-40 down before battling back to level the match.
He took a 2-0 lead in the third and sealed his best result since losing to Novak Djokovic in the quarterfinals in Monaco.
Cilic romped into the last four with a 7-6 (7-4) 6-4 win over Janko Tipsarevic, and now has a 5-0 career record against the Serbian.
In Friday's opening match, world No. 8 Berdych crashed out as he lost 6-4 3-6 6-2 to Belgium's world No. 62 Xavier Malisse.
Malisse will next take on eighth seed Marcos Baghdatis after the Cypriot ousted Spanish No. 3 Fernando Verdasco 7-6 (7-3) 6-4.
Berdych was playing his first tournament since losing in the final at Wimbledon in early July.
The Czech said he would not return to the tournament, being unhappy to have to play in mid-afternoon just 10 hours after his previous match.
"This is a pretty bad experience for a tournament where I'm first seeded. I thought I could get some better times with a No. 1 seed," Berdych told reporters.
"It's the reason I'm not going to be here next year. In the first set I felt like I was still sleeping. I was not 100 percent ready and that's disappointing. I wanted to play better."
Meanwhile, second seed Samantha Stosur failed to reach the semifinals of the women's San Diego Open, losing 6-4 6-3 to Italian Flavia Pennetta on Friday.
The fifth seed's reward for eliminating the French Open runner-up is a clash with Russia's two-time Grand Slam champion Svetlana Kuznetsova, who defeated American teenager CoCo Vandeweghe 7-5 6-2 after trailing 5-2 in the opening set.
Polish fourth seed Agnieszka Radwanska thrashed Israeli No. 7 Shahar Peer 6-2 6-0 to earn a semifinal with Slovakia's Daniela Hantuchova, who came from behind to beat young Russian Alisa Kleybanova 2-6 6-4 6-3.
World No. 3 Caroline Wozniacki reached the final of her home Copenhagen Open on Saturday, with the Danish top seed beating Russia's Anna Chakvetadze 6-1 2-6 6-4.
She will play seventh seed Klara Zakopalova on Sunday after the Czech upset China's No. 2 Li Na 6-3 1-6 6-4.