World No.1 Lorena Ochoa was flawless for the second day in a row on Saturday, firing a seven-under 64 to take a four-shot lead in the US$2.25 million Canadian Women's Open.
Taiwan's Tseng Ya-ni was six shots off the pace in fourth place after signing for a 67. Tseng sank three of her five birdies on the back nine after recording her lone bogey of the day at the ninth.
After firing a 6-under 65 on Friday, Ochoa outdid herself at the Royal Mayfair Country Club, sinking five birdies on the front nine and two more after the turn to sign for a 199 after 54 holes.
The Mexican star, who entered the day one shot behind Juli Inkster and Shi Hyun-ahn, is fresh off winning her first major title -- the British Open on Aug. 5.
She is looking to add to her tour-leading four wins and 14 top-10 finishes in 17 events this year and said the rainy conditions, expected to continue yesterday, were no hindrance.
"I actually love the rain," she said. "It has been good to me. For some reason I just feel very comfortable. I started with a birdie on my second hole and gathered momentum from there. So here I am, in good position for tomorrow, and that's all that matters."
"The course was playing longer today, and I was able to be in good position from the fairway," she said. "I was thinking about the course record. It didn't happen, so I have one more day tomorrow."
Inkster shot a two-over 73 to fall into a tie for fifth at 207, while Ahn also struggled, finishing the day at three-over for 208.
Americans Paula Creamer and Laura Diaz were within reach of Ochoa at 10-under 203.
Both also signed for bogey-free rounds, with Creamer shooting a 66 and Diaz carding a 68.
Creamer continued her hot play after birdying her final four holes on Friday.
In her third year on the LPGA Tour, she birdied four and six before the turn and added three more on the back nine, including two on par-threes.
"I played good, I think I missed two greens today," Creamer said. "I missed a ton of opportunities out there, but considering the conditions, I'll take five-under."
While Creamer's excellent effort left her even further behind Ochoa, the young American said she couldn't worry about that heading into the final round.
"You can only control what you do on the golf course, you can't control anybody else," she said. "I know that today was kind of a moving day, and as long as I'm somewhat in contention tomorrow, I'm pleased with that. What are you going to do? I played good, and obviously Lorena played good, too."
Kimberly Hall was tied with Inkster after bogeying her final two holes en route to a 72.