Chinese rookie Carl Yuan birdied three of the last four holes to grab a one-stroke lead after Friday's second round of the US PGA Tour's Canadian Open.

Yuan, who missed the cut in eight of his prior 10 tour starts, fired a five-under par 67 to stand on nine-under 135 after 36 holes at Oakdale.

"Definitely played some great golf," Yuan said. "I had the exact same mindset as yesterday. Just go out, play freely, let the result take care of itself and have fun. It works out good so far. I think I'm going to keep that rolling."

England's Tyrrell Hatton, who reeled off five birdies in a row, fired the event's low round with a 64 to match countryman Aaron Rai, Taiwan's C.T. Pan and Canada's Corey Conners for second on 136. Rai and Conners both shot 69. Pan fired a 66.

"I just hit a lot of good shots," said Pan, the Tokyo Olympic bronze medalist. "I gave myself a lot of good opportunities on the greens."

Conners, in the best 36-hole spot by a Canadian since 2004, hopes to be the first host-nation winner of the event since Pat Fletcher in 1954.

"Having a lot of fun," Conners said. "Hopefully can keep hitting it well and get some more putts to fall in over the weekend.

Free-swinging golf was Yuan's plan this week rather than a specific score.

"I try to make the swing. Just let the body take care of itself," he said. "Normally that works out great. I've been way too technical in past events on tour this year."

World number 164 Yuan made only five cuts in 16 prior season events, but produced his best 36-hole start since placing 21st in January at Hawaii. His best PGA finish was a share of 17th at Shanghai in 2019.

Yuan, 26, birdied from just inside 14 feet and just outside 12 feet on the first two holes before a bogey at three. He birdied the par-5 seventh and 12th holes on four-foot putts before a bogey at 13 after missing the green with his approach.

Yuan closed in style by sinking a 12-foot birdie putt from the fringe at 15 and a four-foot birdie putt at 16 then pitching to four feet to set up a birdie putt at the par-5 18th.

World number 16 Hatton, a top-20 finisher in his past five starts, answered a bogey at the sixth hole with birdies on the next five holes to match his longest PGA Tour birdie streak.

"A lot of putts went in, which was nice," Hatton said. "The greens were a bit funky this afternoon. I managed to hit my start line, they would bobble off line and thankfully they bobbled back on line and went in."

Hatton, a six-time European Tour winner, captured his only US PGA title in 2020 at Bay Hill but was second at this year's Players Championship. (AFP)