ARDMORE, Pa. — Tiger Woods made birdie at the first hole, only to watch his day go racing downhill from there.

By the time it was over, Woods skidded to seven bogeys and a 6-over-par 76 Saturday, tumbling down the leaderboard and matching his worst round as a pro at the U.S. Open. That left him 10 strokes behind third-round leader Phil Mickelson, the only player under par at the short but devilishly tough Merion Golf Club.

Despite leading the PGA Tour in putting in recent weeks, Woods needed 36 putts on the severely undulating greens. He blamed his inability to gauge the speed of those baffling putting surfaces for his three days of uneven play — and he was right.

Woods is tied for third in fairways hit and 22nd in reaching the greens in regulation. But he's averaged 32 putts per round, which left him tied for 53rd in the field of 73 players.

"It's certainly frustrating because I was feeling like I was playing well this week and I just didn't make the putts I needed to make," he said afterward.

"The first two days, I had, like, three 3-putts and I was four shots off the lead, and I missed a boatload of putts within 10 feet. So I really wasn't that far off. If I clean up the round and don't 3-putt, I'm one shot back starting out today. ..." Woods added.

"Basically, I just didn't have the speed right this week and it certainly showed."

Woods' toughest stretch came at Nos. 3-6, where he made three bogeys in a four-hole stretch. He blamed the last of those for setting the negative tone that hung over his round like the storm clouds that rolled over Merion throughout Thursday's opening round. His troubles at No. 6 included a tee shot that finished up in another player's divot in the fairway, as well as a delicate greenside chip that rolled back and left him facing his next shot from farther back.

"I think the (bogey) 5 really turned my round around," Woods said. "I drove it right in the middle of the fairway and I end up in a ball mark from somebody else's ball mark, so it was kind of the way it went."

This U.S. Open marks exactly five years since Woods won his last major, at Torrey Pines, which he captured in a playoff against Rocco Mediate, despite hobbling around with ligament damage. His pursuit of Jack Nicklaus' career record of 18 majors remains stalled at 14.

Woods also shot a 76 in the final round at Shinnecock Hills in 2004, as well as two rounds of 76 at Winged Foot in 2006 when he missed the cut.

Woods' worst round ever at an Open was a 77 at Oakland Hills in 1996, when he was a 19-year-old amateur.

What made his performance here perhaps even more surprising is that Woods has already won four times this season, including The Players Championship — sometimes called golf's fifth major — and three of his last five starts. Most recently, however, Woods stumbled to an 8-over-par finish and a tie for 65th at the Memorial, a tournament he'd won five times.

Woods said several tough pin placements chosen by the U.S. Golf Association's course set up compounded his problems trying to figure out the speed of the greens.

"Look at what they did at (Nos.) 7 and 8 today. Couple short holes, but 7 is one step and a half over the top of the ridge. Eight is on the down slope a little bit, and it's a pretty steep slope. So they got some really tough ones out there," he said.

But Woods' also conceded he rarely put his approach shots into those greens where he should have.

"If you put the ball in the right spots you've got uphill putts and you can be really aggressive," Woods said.

Woods now faces the prospect of beginning the final day of yet another major with only the longest of shots to contend. What little consolation he could muster came when someone asked, "Tough day?"

"Yeah," Woods replied. "At least I started well."