MONTREAL -- There will be no repeat of the 2013 men's Rogers Cup when Canadians Milos Raonic and Vasek Pospisil delighted the Uniprix Stadium crowd by both reaching the semifinals.

Pospisil did his part, beating qualifier Lu Yen-Hsun 6-4, 6-3 in a first-round match at the $US4.1 million event on Tuesday.

But Raonic, in his first action in a month since returning from a pinched nerve in a foot, came out on the wrong end of a 7-6 (1), 7-6 (1) decision against Ivo Karlovic in a battle of towering sluggers.

Vernon, B.C., native Pospisil will try to keep his Rogers Cup going in the second round against American John Isner, the 16th seed who survived a 6-4, 6-7 (6), 6-3 encounter with Benjamin Becker.

Isner was playing only two days after losing in the final of an event in Washington, D.C. to Kei Nighikori. He beat Pospisil in two sets in the round of 16 of that event, although the Canadian holds a 3-2 edge in their career head to head meetings.

"I played him enough times to know what to expect," said Pospisil. "He can say the same thing, I guess. So definitely that's a pretty open one."

Pospisil had his breakthrough moment the last time the men's event was held in Montreal in 2013. He upset Isner in his first match, then beat Radek Stepanek and sixth-ranked Tomas Berdych. He got to the semifinals when Nikolay Davydenko retired with an illness.

It ended with a loss for Roanic, but the performance put Pospisil into the world's top 40 for the first time. Raonic, of Thornhill, Ont., lost in the final to Rafael Nadal.

Pospisil is on the way back from wrist trouble following a strong performance at Wimbledon, where he reached the quarter-finals.

"After winning (on Tuesday), I had a couple of flashbacks to 2013," said Pospisil, currently ranked 45th. "It was such a special week for me.

"But that's good. I can just take positive things from that. A deep run is definitely something that I want to achieve this week. That's kind of the goal."

The six-foot-five Raonic and six-foot-11 Karlovic hammered serves at each other, with the Croatian winning the ace battle 22 to 12. Karlovic passed the 1,000 career aces mark. He is second all time to Goran Ivanisevic (10,183).

Top-seeded Novak Djokovic took his second round match 6-3, 7-6 (4) over Thomasz Bellucci for his 250th career win a Masters 1000-level event. And defending champion Jo-Wilfried Tsonga, seeded 10th, got through the first round 6-4, 6-4 over Borna Coric.

Nick Kyrgios outlasted veteran Fernando Verdasco 6-3, 4-6, 6-4 with his fellow Australian Lleyton Hewitt looking on. There are rumours that Hewitt is now coaching the 20-year-old, but Kyrgios said: "He's definitely not my coach, let's clear that up now. But he's definitely helped me out, which is really good."

He advanced to a second round meeting with third seeded Stan Wawrinka, who beat him earlier this year on a grass court.

It was a short Rogers Cup for Frank Dancevic of Niagara Falls, Ont. who lost 6-2, 6-4 to Pablo Andujar.

"I felt like, leading up to this tournament I was playing pretty well," said a dejected Dancevic, a wild card entry into the Rogers Cup whose world ranking has plummeted to 213th in a frustrating season.

David Goffin, seeded 13th, made quick work of Steve Johnson 6-2, 6-2 when play began after a rain delay, and 14th seeded Grigor Dmitrov downed Alexandr Dolgopolov 6-4, 7-5.

Richard Gasquet, the 11th seed, withdrew with an illness.