Nick Kyrgios’ US Open build up is off to a rocky start after he was beaten by 17-year-old Canadian Denis Shapalova at the Toronto Masters.

Barely a fortnight after winning the junior Wimbledon title, Shapalova showed more signs of a bright future with a 7-6 (7-2) 3-6 6-3 first round defeat of Kyrgios on Monday.

The loss to the world No.370, which barely took 90 minutes, left the 11th-seeded Aussie puzzling over his continual scratchy form and occasional lack of apparent desire on court.

Kyrgios was plagued by 18 double-faults while hitting 13 aces as he played his first match since a fourth round Wimbledon loss to Andy Murray.

Shapalova was playing only his second ATP event after losing last week in the opening round in Washington.

Kyrgios’ defeat was balanced by success from compatriot Bernard Tomic, as the 12th seed beat Alejandro Gonzalez of Colombia 6-4 7-6 (7-0).

“I feel like here’s a good chance for me,” Tomic said.

“I really have to focus and really go for my shots and relax if I want to make a quarter or semi.”

Shapalova next faces Grigor Dimitrov, after the Bulgarian flirted with an early exit but rallied in the nick of time to beat Japan’s Yuichi Sugita 5-7 7-6 (7-5) 6-4 in two and a half hours.

Dimitrov, who lost six straight matches before making the third round of Wimbledon, turned the corner in Canada as he won a lob duel while trailing 4-1 in the second-set tiebreaker after losing the opening set.

Two more Canadians posted wins as Steven Diez beat Briton Kyle Edmund 3-6 6-3 6-2. Peter Polansky overcame Tim Smyczek 4-6 6-3 6-0.

Ninth seed John Isner started with a win over Dudi Sela 4-6 6-3 6-2.

Croatian Borna Coric stopped countryman Ivan Dodig 5-7, 6-4, 6-2.

Elsewhere in the first round, South Africa’s Kevin Anderson ended a three match losing streak with a defeat of Viktor Troicki 7-6 (7-4) 6-3.