The eight-seeded Nishikori will face Janko Tipsarevic of Serbia, who advanced after Nikolay Davydenko of Russia retired with a left hip injury just four games into their match. The third-seeded Tipsarevic was leading 3-1.
"I don't know what the injury is exactly yet," Davydenko said. "I'm a bit scared as I've never had anything like it before. I will still go to Beijing, maybe wait a few days and see what the pain is like."
The second-seeded Troicki failed to serve out the match at 5-2 in the second set but held on for victory at Putra Stadium. Troicki is looking for his first title of the year after losing the final in Sydney in January.