0351 GMT December 14, 2017
The 18-year-old Shapovalov, who needed a wild card to get into the tournament, continued his giant killing form at the hardcourt tournament by rallying to beat Nadal in three sets, 3-6, 6-4, 7-6 (7-4) on Thursday, FOX Sports reported.
Nadal would have returned to No. 1 in the world if he had defeated Shapovalov on Thursday and Adrian Mannarino on Friday.
The defeat means injured Brit Andy Murray will hold on to top spot for now.
Shapovalov is youngest ATP World Tour Masters 1000 quarterfinalist ever and second youngest player to defeat Nadal since Borna Coric did at 2014 Swiss Indoors.
Nadal went 0-for-6 on break points in the third set, sat back and waited for the kid to miss. He didn't.
Shapovalov’s stunning upset against the reigning French Open champion came as a result of some inspired tennis in front of a boisterous home crowd who cheered his every shot.
Shapovalov had just three wins this season coming into the tournament. He quickly got on a roll in Montreal beating Brazil’s Rogerio Dutra Silva in the opening round 4-6, 7-6 (10-8), 6-4.
He defeated former US Open winner Juan Martin Del Potro in the second round in straight sets 6-3, 7-6 (7-4) to set up the showdown with Nadal.
Shapovalov won seven of the final eight points of the third set tiebreaker before closing out the match with a forehand winner down the line. He celebrated by falling onto his back then covering his face with his hands.
Shapovalov blasted a total of nine aces, including ones on his second serve that handcuffed Nadal. He also had seven double faults and won 67 percent of his first serve points.
Nadal won 77 percent of his first serve points but had just two aces and six double faults in the two hour, 45 minute center court match.
"I was just swinging for the fences," said Shapovalov after his triumph over world No. 2.
"The whole day I was like: there's no chance, I will go and have fun but there is no way I am beating this guy," Shapovalov added.
The 31-year-old Nadal praised the teenager’s performance, saying, "He played well. He has great potential,"
"I wish him the best. He played with the right determination."