Canada fought back to end day one of their Davis Cup World Group tie against Great Britain level at 1-1 in Ottawa.
Dan Evans beat 17-year-old Denis Shapovalov 6-3 6-3 6-4 in the opening singles, before Vasek Pospisil upset Kyle Edmund 6-4 6-1 7-6 (7-3).
Pospisil, ranked 86 places below Edmund at 133rd in the world, overcame a leg injury to level the best-of-five tie.
Jamie Murray and Dom Inglot are scheduled to face Daniel Nestor and Pospisil in Saturday’s doubles contest.
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The two nations are missing their leading players as world number one Andy Murray recuperates following the Australian Open, while Canada’s world number four Milos Raonic is injured.
“We had a video from Andy last night and (captain) Leon (Smith) put it on the big screen,” said Evans.
“I’m guessing he was watching. He said he would be. It’s obviously nice he supports the team. He’s a good guy to have in our corner.”
Number one Evans puts Britain in front
Evans successfully carried the responsibility of being Britain’s number one as he converted a gulf in experience over world number 234 Shapolavov into a straight-sets victory – the Briton’s first win in a live Davis Cup rubber since 2013.
Shapovalov gave evidence that that he has a bright future, the Wimbledon junior champion hitting plenty of flashing winners behind a swinging left-handed serve, but 39 unforced errors proved too much.
The Canadian dropped serve in a nervous opening game and again to lose the set, but he threatened more in the second and it took an ace and a deft drop volley for Evans to see off the first two break points against him.
That was as close as Shapovalov would get, however, with Evans then breaking thanks to a fantastic lob and making the decisive move at 4-3 in the third set.
“I tried to get on top early,” said Evans. “That was the plan, to come out and silence him and not give him confidence. I did that and then rolled him from then on. I was happy with way I played.”
Pospisil too strong for Edmund
Edmund, ranked 47th, looked a good bet to increase Britain’s lead against Pospisil, who has slipped from 25th three years ago to a lowly 133rd in the world.
The Canadian, 26, was further hampered by a left leg injury which required a medical timeout as early as the fifth game, and continued to require bouts of treatment.
It was therefore all the more remarkable that Pospisil reeled off eight of nine games following the timeout with some fine serving, while Edmund produced an error-strewn performance across the net.
The fast pace of the court allowed Pospisil to keep the points short, race through his serving games and put pressure on the increasingly vulnerable Edmund serve.
Edmund, 22, managed to get through to a tie-break in the third set but was outplayed once again, ending with eight double faults and 39 unforced errors.
Russell Fuller, BBC tennis correspondent:
There was real composure, confidence and style in the way Evans defused the challenge of his 17-year-old opponent. Having saved the only two break points he faced midway through the second set, Evans then pounced immediately to secure the only break required to win the set.
Edmund, in contrast, put in a very ragged performance against Pospisil, who has had a miserable time in singles these past 12 months. The Canadian was in excellent form, serving 19 aces and getting the very best out of the quick court laid over the ice rink here in Ottawa.
Murray and Inglot have been warned: Pospisil will play again in Saturday’s doubles, and his partner Daniel Nestor is a former Olympic champion, world number one and multiple Grand Slam champion.
World Group latest
World number two Novak Djokovic is the only member of the top 10 in action and he trailed by a set and a break against Russia’s Daniil Medvedev, before the 20-year-old was struck down by cramp to give Serbia a 2-0 lead.
Djokovic, playing for the first time since his shock second-round loss to Denis Istomin at the Australian Open, had earlier needed treatment to his right shoulder.
“The pain I had prevented me from playing the points as I wanted to,” said the 12-time Grand Slam champion, who led 3-6 6-4 6-1 when Medvedev retired.
“But it’s a good victory and we are in a very good position.”
The winners of the tie in Ottawa look set to face a trip to France in the quarter-finals, after Yannick Noah’s side took a 2-0 lead over Japan in Tokyo.
Argentina’s Davis Cup defence could be short-lived without star man Juan Martin del Potro, as they trail 2-0 to Italy in Buenos Aires.