A rejuvenated Roger Federer believes he is still reaping the benefits of his extended break from tennis after a comfortable opening victory at the ATP Montreal Masters gave him his best start to a season since 2006.

The Swiss star, who celebrated his 36th birthday on Tuesday, swatted aside Canada's world number 116 Peter Polansky 6-2, 6-1 in just 53 minutes to book his place in the second round.

Federer is riding high after a spectacular year which has netted him both the Australian Open and Wimbledon crowns.

On Wednesday's evidence few would bet against him adding the US Open to that haul after a masterful performance that left Polansky groping at shadows.

A one-sided win gave him a 32-2 start to the season, his best beginning to a campaign since 2006 when he began 38-2 and finished the year at world number one.

Federer attributed his renaissance to rediscovering full fitness after knee surgery in 2016 and taking a two-month break from the game earlier this year.

"I guess for me the key is that I'm actually healthy," Federer said.

"I knew that when I was healthy, I was going to be able to have chances to win slams again, to play against the best, beat the best.

"That's also reasons why I'm still playing today. If I felt like I couldn't do all these things, it would not be enjoyable or I wouldn't be doing it any more.

"I think the belief was always there. The body always needed to be there, too. I think the break just rejuvenated me ... I came in refreshed. It was a different mindset."

Federer took control immediately against Polansky, holding his opening service game comfortably before quickly going 0-40 up in the second game.

A Polansky double fault gave Federer the break and the Swiss was soon 3-0 up after holding serve to love in the next game.

Polansky held his next two service games but never looked like breaking Federer's serve as the veteran moved into a 5-2 lead.

Federer then broke Polansky to take the first set, following a signature backhand with a deft forehand volley that left the 29-year-old Canadian scrambling.

Federer was soon in control in the second set, scoring an early break and holding twice to move 3-0 up before a further break made it 4-0.

Polansky earned a stay of execution after holding serve in the sixth game to make it 5-1, but Federer raced into the next round with a comfortable hold, finishing with an emphatic overhead smash.

Federer will face either American Jack Sock or Spain's David Ferrer in the third round.

Elsewhere Wednesday, France's Gael Monfils saved four match points before digging deep to defeat Japanese fifth seed Kei Nishikori in an attritional three-set duel.

Monfils prevailed 6-7 (4/7), 7-5, 7-6 (8/6) to advance.