Kevin Na birdied his last five holes on the way to a blistering 9-under 63. (Chris McGrath/Getty Images)

Retief Goosen held the early lead, but it was 25-year-old Kevin Na who turned heads after a water-logged Thursday at the Canadian Open.

Na birdied eight of his last 10 holes on the way to carding a 9-under-par 63 at the Glen Abbey Golf Club in Oakville, Ont., after a lengthy delay nixed plans to complete first-round play on Thursday.

Goosen, who eagled his first hole after a seven-hour and 32-minute rain delay, had an early lead at the turn after playing the back nine at 5-under.

But he slowed down on the front and finished at 7-under, good for a second-place tie with Scott Verplank and Joe Durant after their first rounds were finished.

"We got lucky this afternoon," said Goosen. "You know, when the storm moved through, the conditions were perfect — perfect playing conditions."

Na's assault on the leaderboard came during the front nine. Na, who started his round on the back nine, shot a 7-under 28 in the second half of his round.

It matched Vijay Singh for the lowest nine-hole score ever in the history of the Canadian Open, done on the same nine holes back in 2004. Na birdied his final five holes and finished his round just before play was halted because of darkness.

"The greens are holding, so you can get aggressive with the irons," Na said. "But off the tee, you must put yourself in the fairway. The rough is very thick."

He hustled to finish so that he didn't have to return early Friday.

"That's all I was hoping for," Na said. "I was just trying to get to the tee real quick and hit. Ended up being we had 10, 15 minutes to spare, but you never know when they're going to call it."

Mike Weir finished at 1-under, eight shots back of the leader. (David Donnelly photo)

Mike Weir of Bright's Grove, Ont., was tied for the lead with Goosen in the early going but faltered down the stretch. He finished with three bogeys in his last seven holes to drop to 1-under, good for a tie for 37th.

"I had a tough time finding my rhythm today for some reason," said Weir. "Maybe all the waiting around and getting warmed up and then getting pushed back another hour [caused trouble]."

Heavy rain halted first-round play at 8:38 a.m. ET, with only 52 of the 156 golfers in the field having had a chance to play one hole or more before the delay.

Play resumed at 4:10 p.m., and golfers made mincemeat of the rain-softened course.

"You know, it's not what we wanted for this event," said Weir. "It's kind of playing soft — a dart show.

"It's too bad because the course is really good; it's in really good condition."

Calgary's Stephen Ames only managed to get two holes in before play was halted, and will have to finish his first round on Friday. He was at 1-under.

Bryan DeCorso and Chris Baryla were the top Canadians on Thursday, both at 3-under with three holes to go in their rounds.