In the featured pairing of the morning, three-time champion Tiger Woods easily outplayed partners Phil Mickelson and Bubba Watson at the 112th U.S. Open at Olympic Club.
Woods put together a round of one-under 69 and is three strokes off the early lead.
Mickelson, a five-time runner-up, got off to a rough start as his opening tee shot on the ninth got stuck in a tree and he had to walk back to the tee and reload. He managed to save bogey, but he also bogeyed his next two holes en route to an opening six-over 76.
Watson started with bogeys on two of his first three holes. The Masters champion managed just one birdie in a round of eight-over 78.
Woods, who has won two of his three U.S. Open titles in California, started with five straight pars. He tripped to a bogey on the 14th, but rebounded with a birdie on the par-five 17th.
After four more pars, Woods carded back-to-back birdies on four and five to get to minus-two. He stumbled to a bogey on the sixth, then parred his final two holes as players are starting on the first and ninth this week.
"Today was tricky. I don't know what they did overnight, but they sure sped up this golf course," Woods said in a televised interview. "The greens were springy, the fairways came alive, and some of the clubs we were hitting in the practice rounds were out the door. I had to make adjustments on the fly."
The one-under 69 was the first sub-par opening round at the U.S. Open for Woods since he carded a three-under 67 in 2002 on the Black Course at Bethpage.
Mickelson steadied himself after his first three bogeys. He rolled in a birdie effort at 13, but gave that stroke right back as he bogeyed the 14th.
At the long par-five 16th, the longest in championship history at 670 yards, Mickelson missed the green with his third and his fourth. He managed to save bogey as he headed to the front side at plus-four.
Mickelson parred five in a row starting at 17. He stumbled to bogeys at four and five to slide to six-over, then parred his last three holes.
All five of Mickelson's runner-up finishes occurred on the East Coast, while he finished in the top-18, including a tie for 10th at Olympic in 1998, at the last four Opens in California. Mickelson's 76 was his worst in a major since he carded a 77 in the third round last year at Congressional.
After his first two bogeys, Watson dropped shots at 15 and 16 to fall to four- over through his first eight holes. Like Woods, Watson birdied the 17th, but he faltered to a double-bogey on the par-four 18th.
On the front side, Watson tripped to bogeys on two and three. He faltered to his final bogey at the sixth, which left Watson at plus-eight.
That was his worst round in a major since closing with a 78 at the 2011 Masters.