Second seed Gael Monfils withdrew from the San Jose Open tournament on Friday after defeating American wild card Tim Smyczek 6-4, 7-6 in the quarter-finals.
The Frenchman aggravated an injured left wrist in his win over Robert Kendrick on Thursday and after beating Smyczek a day later, determined he was unfit to continue.
"It's been a month-and-a-half that I've had this pain," Monfils said. "I can't hit my backhand. I tried, but my backhand is very soft. I have a better backhand than I showed here... more powerful."
Monfils has subsequently withdrawn from tournaments in Memphis and Acapulco and a Davis Cup tie, and is expected to miss up to six weeks of action.
"I tried to play a game he doesn't like, with a lot of spin, and it went well," the Spaniard said.
"I played well on the important points, like I did yesterday, which was good too. I knew it would be tough. Denis made it to the semi-finals here last year and the conditions benefit him."
Juan Martin del Potro continued his comeback from a wrist injury that sidelined him for a year with a comfortable 6-2, 6-3 win over Lleyton Hewitt and the Argentine will next face Verdasco in the only semi-final to be played on Saturday.
In form Canadian Milos Raonic advanced to the final four with a 6-4, 7-6 victory over Richard Berankis and is guaranteed a place in the final following Monfils' withdrawal.
Soderling beats Youzhny to stay on course for title
Top seed Robin Soderling beat Mikhail Youzhny 6-4, 7-6 in a reprise of last year's final to reach the last four of the world indoor tournament on Friday.
Defending champion Soderling will now meet unseeded Viktor Troicki of Croatia, a 7-5, 6-2 winner over Marin Cilic, on Saturday.
Soderling, who hit 13 aces, finished off the first set with a break. When Russian Youzhny wasted a chance to take the second set, the Swede struck in the tie-break.
"It was a tough match but so far all my matches this tournament haven't been easy," Soderling told reporters. "Today I felt really strong on the big points and that gave me confidence."
Earlier, Ivan Ljubicic beat Cypriot Marcos Baghdatis 6-4, 6-7, 7-6 to reach the semi-finals where he will face Jo-Wilfried Tsonga, who had a day off as his opponent, Tomas Berdych, pulled out with influenza.
Dolgopolov faces top seed Almagro in Brazil Open final
Red-hot Ukrainian Alexandr Dolgopolov reached his first ATP tour final when he brushed aside Ricardo Mello 6-2, 6-1 in the Brazil Open on Friday.
The Australian Open quarter-finalist will meet world number 13 Nicolas Almagro in Saturday's final after the Spanish top seed overcame Argentina's Juan Ignacio Chela 1-6, 6-2, 6-4 in the other semi-final.
Top seed Almagro will be looking for his second Brazilian title after winning the tournament in 2008. The 25-year-old has enjoyed considerable success on Latin America's claycourts having also won the Mexican leg of the four-tournament circuit in 2008 and 2009.
Hewitt clinches Kooyong Classic title
Defending champion Roddick rolls on at Brisbane
Youzhny wears down Wawrinka
Soderling beats Monfils to claim Paris Masters
Federer downed by Monfils in Paris semi-final