"This is fantastic win for me and my country," Tipsarevic said. "It seems I can't have a match without drama."
Pospisil said he thought he could turn the match around after forcing the third-set tiebreaker.
"I believed I could do it, but obviously it didn't happen," said Pospisil, who broke in tears after the loss. He said he hurt his ankle in his fall as well.
"At that moment, I was in a lot of pain," he said. "Not only physically, but also psychologically."
Djokovic, coming off a four-set loss to Rafael Nadal in the U.S. Open final on Monday, dimmed Canada's chances with one of his trademark displays against the 11th-ranked Raonic.
"This is like the (football) World Cup for us," Djokovic said. "Winning the Cup in 2010 gave us players so much confidence."
Djokovic kept the big-serving Canadian at 10 aces, compared to the 34 he had in his five-set victory against Tipsarevic on Friday, and broke Raonic six times in front of some 10,000 boisterous Serbian fans.
Raonic, apparently struggling with an ankle injury he sustained Friday, put up tough resistance in the first set. But his game started crumbling after being held to a single point in the tiebreaker.
"I felt that I was dealing with anguish and pain," Raonic said. "He really played well in that tiebreaker."