Defending champion Novak Djokovic lost to Andy Murray in the Toronto Masters quarter-finals but Wimbledon champion Rafael Nadal survived a scare to advance on Friday.
Nadal, in his first tournament since his epic five-set win over Roger Federer at Wimbledon, was pushed by Frenchman Richard Gasquet before rallying to claim a 6-7, 6-2, 6-1 victory.
The Spaniard will face Murray on Saturday for a place in Sunday's final after the eighth-seeded Briton shocked Djokovic 6-3, 7-6.
The other semi-final will pit in-form Frenchman Gilles Simon against German journeyman Nicolas Kiefer.
Simon, who shocked Federer in the second round, continued his magical hardcourt campaign, outlasting hard-hitting Croatian Marin Cilic 3-6, 6-2, 6-3 while Kiefer, seeking his first title in eight years, demolished seventh-seeded American James Blake 6-1, 6-2.
Gasquet, who had never beaten Nadal in four career meetings, looked determined to end the drought, battling the world number two to a first set tiebreak and winning it on his sixth set point with a driving forehand winner.
But the effort appeared to drain Gasquet and steel Nadal, who broke to take a 4-1 lead in the second and swept through eight of the next 10 games to finish off the Frenchman in two hours 19 minutes.
"It was an emotional tiebreak, I had my chance but he had more than me and finally he played a little bit better," Nadal, who claimed his first career hardcourt title in Canada in 2005, told reporters.
"He played well but later I improved a little bit my intensity, my rhythm, I start to move him a little bit more and he had a few more mistakes.
"If you win the tiebreak sometimes you start a little more relaxed, so I know this and started the second set 100 percent."
Murray, searching for his first win in five career meetings with Djokovic, broke the Australian Open champion at the first opportunity to move into a 3-0 lead and eased to the opening set.
The players exchanged breaks in the second but Murray dominated the tiebreak, winning it 7-3 to reach the Canadian semi-finals for the second time.
"It's a big win mentally for me," Murray said. "The last three times I played him I lost pretty badly.
"The first time I played him I was a set and a break up and lost. It was pretty much similar to tonight.
"Against the top guys you always expect them to come back, and he did that in the second set.
"But I've been playing well and I felt like I had a chance of winning."