It wasnt Ochoa, who had to rally to break even.
It wasnt even defending champion Cristie Kerr, who finished one stroke better.
No, one of the stars on the first day of the most prestigious event on a female golfers schedule was the unknown member of this high-profile trio, an amateur from Colombia named Maria Jose Uribe.
She shot a 69 on Thursday and was tied for fourth place, two strokes behind leaders Ji Young Oh and Patty Hurst.
Im not going to think about the scoreboard right now, said Uribe, who will be a sophomore at UCLA in the fall. Its four days, so Im just having fun out there.
Surely there were some nerves at work, while tackling the longest course in tournament history next to the top-ranked player in the world of womens golf.
Well, youre always nervous, but I like that, Uribe said. I like to play under pressure, so I was looking forward to it and I knew that I was going to play good today.
This 18-year-old, who won the U.S. Womens Amateur last summer, said she thrives off the challenge of stiff competition.
Every time Im under pressure I do better than when Im just playing for fun and stuff, Uribe said. If you play with me on a Saturday in my golf course, I know that you wont think that Im a good player.
Ochoa is one of Uribes two heroes in the sport. Tiger Woods is the other.
Though eight years and millions of dollars apart, Ochoa and Uribe frequently chatted with each other while they walked the fairways. Sharing the loose bond of being from Latin countries, they hit it off during their first time playing together.
I was laughing and it was just very nice and easy to watch her play. She seemed very relaxed, said Ochoa, who also remarked about Uribes proficiency speaking English.
Well, she still barked instructions to her ball in Spanish.
Derecha, por favor! Uribe yelled, while trying to coax her tee shot on the 16th hole to the right.
Ochoa clearly cemented Uribes impression of her as someone to look up to on the tour, whenever she joins it.
It was a great experience for me, Uribe said, adding: Shes like super nice.
After spending two years at the International Junior Golf Academy in Hilton Head, S.C., Uribe returned to her hometown of Bucaramanga for her senior year of high school before enrolling at UCLA. She said shes committed to finishing college, unless of course something unexpected happens.
If I like win the U.S. Open or something like that, she said.
This was a step in the right direction.
Editor's Note: Don't miss the live U.S. Women's Open blog, as well as other championship coverage, from partner Golf for Women magazine at golfforwomen.com.