Michelle Wie had to think her 6-under-par 65 would hold up despite a strong wind whipping through Grey Silo Golf Course.
It should have been enough, until defending champion Hee Young Park caught fire.
The South Korean made her move over the last 10 holes, draining four birdies to match Wie's score after Thursday's first round of the Manulife Financial LPGA Classic in Waterloo, Ont.
Wie, who matched her lowest round of the season, birdied three of the last four holes including an eight-foot downhill putt on No. 18. She said she had the same mindset as last season — getting out of the gate with a good score in case other golfers continued to go low at Grey Silo.
"That's definitely what I thought today," said Wie, who was off the course before Park started her round.
"I was early off and I wanted to just make a lot of birdies early on, especially with 26 under winning it last year, it's definitely one of those golf courses where you may have to keep making birdies. I went 6 under today and it's not enough.
"I have to keep making birdies for the rest of the weekend. I still have my work cut out for me."
Park, who equalled her opening round score last year when she won with the second lowest score in LPGA history at 26 under, said she surprised herself by grabbing a share of the lead.
"I didn't really expect to play well today, because last year and this year pretty different golf conditions — this year more wet and not firm," Park said. "We played a month earlier than last year, so it was a more windier course condition.
"We didn't care about other players playing well or not, just one-by-one shot playing."
Park laughed when asked if she could equal her score from last year.
"I hope so," she said. "Today, I was a bit lucky.
"I didn't really miss my second shots, so that I hit the green and had a lot of chance to birdie putt. Also, I tried to put it so I had some uphill easier putts rather than hit it too aggressive downhill."
The twosome were one shot better than China's Shanshan Feng and two shots ahead of China's Xi Yu Lin and Christie Kerr of the U.S. at 4 under.
After the top five, 12 players were tied at 3 under.
For the first time in three years at the tournament, the wind factored into the scoring as only five players shot better than 3-under par in the first round. Last year, 22 players opened with lower scores.
Wie was a measure of consistency though on the day with seven birdies, despite some whipping wind, with her only blemish coming with a bogey on No. 9.
"I was consistent and I felt that I judged the wind pretty well today," Wie said. "Tuesday practice round was a lot windier, so I think that was very helpful."
Feng had a strong round with five birdies, but she wasn't able to match the leaders down the stretch.
"Well, this course is normally a birdie course, so everybody's going to make a lot of birdies," Feng said. "Today, I think the wind picked up a little, so the course was playing longer.
"I missed a lot of birdie putts, but I stayed patient and I think that was the key."
Even though most of last year's field had some ridiculously low scores, Feng missed the cut by one. Though she scrambled at times in the first round, biding her time was the key to shooting a low score.
"This year here, I'm not giving myself any pressure," Feng said. "Make it and make it.
"If I don't make it, it's still OK."
'Tough with all the wind'
It was a tough day for the world's top three players. Top-ranked Stacy Lewis and No. 2 Inbee Park finished at 2-under par, and Lydia Ko, sitting in third in the rankings, came in at 1 over.
Sixteen-year-old Brooke Henderson of Smiths Falls, Ont., was the leader among Canadians at 1-under 70. Sue Kim of Langley, B.C., and Jennifer Kirby of Paris, Ont., were at even-par 70, while Charlottetown's Lorie Kane, Erica Rivard of Tecumseh, Ont., and Alena Sharp of Hamilton were at 2-over 73.
Maude-Aimee Leblanc of Sherbrooke, Que., finished at 3-over 74, while Toronto's Rebecca Lee-Bentham and Nicole Vandermade of Brantford, Ont., shot 4-over 75.
Henderson also found the wind to be a factor during her round. she finished tied for 35th last year at 10 under.
"It's tough with all the wind out there," said Henderson, who finished tied for 35th last year at 10 under.
"It's strong and you have to be really careful in club selection and everything. First goal is to make the cut and 1 under, hopefully, will put me in a good position going into tomorrow."
Henderson admitted she is a different golfer than she was two years ago in her first LPGA event.
"When I was 14 playing the Canadian Open I was definitely a little scared mouse, that's for sure, but I'm definitely a lot more comfortable and my game is a lot better, which really helps."