Croatian Ivan Dodig stunned second seed Rafael Nadal on Wednesday, beating the Spaniard in his opening match at the Montreal Masters 1-6, 7-6 (7/5), 7-6 (7/5).
After dropping the first set, the 41st-ranked worked to turn things around and completed his comeback after just over three hours with the aid of 19 aces and three breaks of Nadal's serve.
Nadal took to the court battling a sinus infection but ran away with the opening set.
That's exactly when Dodig began to dig in, his serve getting him out of trouble on repeated occasions.
"This is the biggest win of my career, of my life," said an excited Dodig. "I enjoyed it so much.
"I was fighting hard for every point. In the end I managed, I'm really happy."
Nadal, a two-time Canada champion in 2005 and 2008, was unable to serve out the win, as Dodig took it into a third-set tiebreaker and came back from 0-2 down.
The Croatian has had a breakthrough year, winning his first ATP World Tour title at home in in Zagreb and climbing into the top 50 from 88th at the start of the season.
Nadal's loss was his ninth this season against 51 wins. He had not played since losing the Wimbledon final to Novak Djokovic, who displaced him as world number one.