KOHLER - Fist pump after fist pump, Michelle Wie made Blackwolf Run look more and more like a regular tour track Friday afternoon at the U.S. Women's Open. The 22-year-old Hawaiian shot a 6-under-par 66, tying her for the third lowest round in history and placing her one shot back of Norwegian Suzann Pettersen.

Pettersen is the 36-hole leader after firing a 4-under 68, leading a wave of 19 rounds under par and five rounds in the 60s's in just the morning groups.

On Thursday, there were just 14 rounds under par all day, including just three in the 60's with another 30 rounds topping 80. Heading into this tournament, all players heard about was how it was the hardest U.S. Women's Open in the last 15 years, how 6-over was only good enough for a playoff back in 1998.

Players approached their practice rounds with caution, but once they put the peg in the ground for real on Thursday, they attacked.

"I was trying to find out what was so hard to this course," Pettersen said. "Obviously they lengthened it 400 yards since 1998. But the rough is doable. The greens aren't as firm as what they were back then, from what I've understood, and it's pretty straightforward. Off the tees, it's very - I mean, it's probably as well as the U.S. Open is going to get. Pretty big greens. If you like putting, you're going to get a lot of good chances out here."

World No. 1 Yani Tseng, who admitted being scared of some of the hazards during her practice rounds, discovered there hasn't been much to fear.

"Yeah, just found out the course is not as hard as we thought," she said. "The fairways quite firm and the ball rolls a lot. So we don't hit many like long irons today. So it was easier than I expect, but maybe - I don't know. There always can make some more birdies out there."

With all the red numbers on the leaderboard, the prevailing thought is the United States Golf Association will make things a little more difficult on the weekend.

"I think you're going to see some different pins on the weekend," said Cristie Kerr, who is tied for second with Wie at 4-under. "I think they've been pretty generous with the pins so far, and I can tell you I don't think the USGA is going to like that there were so many low numbers the first couple days. So I think you might see a different course this weekend.

"With that being said, 5-under is leading after two days, which is nothing, comparatively. I mean if it was really low scoring, 10 or 11-under would be leading, but it's not. It's an Open. We're very close to par still, and this course will show its teeth this weekend."