Novak Djokovic secured a place in the final of the Rogers Cup in Montreal when Jo-Wilfried Tsonga retired because of injury when trailing 6-4 3-0.
It resulted in the world number one's 52nd win in 53 matches in 2011 as he chases his ninth title of the year.
Tsonga lost serve in the second set and withdrew after problems with his arm.
Djokovic will play Mardy Fish in Sunday's final after the American beat unseeded Janko Tipsarevic 6-3 6-4 to reach his third final in a month.
Tsonga had won five of his previous eight meetings with Djokovic, and had beaten Roger Federer in the third round, but he racked up 16 unforced errors in the first set.
The Frenchman called for the trainer after losing his serve early in the second set but decided he could not continue and the match ended after 59 minutes.
"It was difficult for me to hit the ball well and hard. That's why I took this decision," said the 26-year-old.
"I don't have the pretension to beat Novak without my arm."
Serb Djokovic said: "He seemed to be struggling with his movement. He told me he had been carrying that injury for a while.
"I'm raising my level with each match," the 24-year-old added. "Becoming number one has been my goal all my life. Now I've achieved my dream. I have no reason to be afraid of what is coming next.
"Everything is a new experience and a challenge."
World number eight Fish, the highest-ranked United States player, is aiming to become the first American to win the Rogers Cup since Andy Roddick in 2003.
The 29-year-old won the Atlanta Tennis Championships title and was runner-up at the Farmers Classic in Los Angeles in July.
"I'm obviously extremely pleased with the way I played," said Fish after seeing off Tipsarevic in 76 minutes with six aces and three breaks of serve.
Fish, who failed to win a match in previous visits to the Rogers Cup in 2003 and 2008, said: "It felt like I had the upper hand for most of the match. Minus a small serving hiccup, I think I played very well."