At least on Saturday, she caught her.
Norway's Pettersen, coming off a playoff victory over Ochoa last weekend, birdied the final four holes Saturday to charge into a tie with the Mexican star in the Samsung World Championship.
Pettersen shot an 8-under 64 to match Ochoa at 12-under 204 through three rounds at Big Horn Golf Club.
"Obviously this year, winning six tournaments, she is the world's No. 1 right now and you always chase No. 1. She is just a very nice competitor," said Pettersen, a three-time winner this year who is a distant second in the player of the year race.
Ochoa, the defending champion in the event for the LPGA Tour's elite players, had a 69 that included a bogey 5 on the final hole when she pushed her drive into a bush for an unplayable lie.
Pettersen finished her round earlier, and thought she probably would be one shot off Ochoa's lead heading into the final day.
Pettersen missed a 15-footer for par on the second hole for her only bogey.
Beginning the day five strokes back, she rolled in a 15-foot birdie putt on No. 1 for the first of her nine birdies.
The 26-year-old Pettersen made four birdie putts from 15-25 feet during her round, and tucked her approach shots near the pin for other birdies.
"My long game I feel is in very good shape. I feel I can be very aggressive from mid irons all the way up to wedges," she said.
Last Sunday in Danville, Pettersen made an 8-foot birdie putt after Ochoa missed her try from 20 feet on the second playoff hole.