Let this serve not just as a warning to second-round leaders Tiger Woods, Jim Furyk and David Toms, but as a reminder to those who barely made the cut on Friday at the U.S. Open.
Strange things happen at U.S. Opens at Olympic Club.
It all started in 1955 when Ben Hogan had finished his 36-hole day at 287. The only player with a chance to catch one of the game's all-time greats was an Iowa club pro named Jack Fleck.
Down two, Fleck birdied the 15th, parred the next two, then made an 8-foot birdie on the 18th to force a playoff. The two went to an 18-hole playoff and the club pro beat the four-time U.S. Open champion 69-72 to complete the historic upset.
Eleven years later, Arnold Palmer built a 3-shot cushion heading into the final round. "The King" went out in 32, amassed a 7-shot margin and appeared destined to win another U.S. Open title.
On the back nine things changed, and quickly.
Palmer made bogeys in bunches and Billy Casper knocked in a couple of birdies and all of a sudden, it was a tournament. Palmer had a 39 on the back and it was another 18-hole playoff.
Casper won that by four, and, much like Hogan before him, Palmer never won another major title.
In 1987, Tom Watson, winless in the three years before his trip to Olympic Club, took a 1-shot edge into the final round. He shot a more-than-respectable 70 on Sunday.
Scott Simpson, a three-time winner on tour, managed a 2-under 68 and made a 6- foot par save on 18. Watson needed a long birdie putt to fall at the last to force a playoff and came up narrowly short.
Watson joined Hogan and Palmer as icons who got trumped at Olympic Club and icons who never again tasted major glory.
Payne Stewart wasn't immune in 1998.
The late Stewart held sole possession of the lead after each of the first three rounds and was five ahead of Lee Janzen, the 1993 U.S. Open winner, with one round to go.
After some early hiccups, Janzen was seven behind.
Stewart stumbled on the back, Janzen shot a spectacular Sunday 68 and he earned his second U.S. Open title.
Stewart got his redemption one year later with a gutsy U.S. Open win at Pinehurst No. 2.
Four Hall of Famers coughed up third-round leads. Some were large and some lost to legit contenders. (Casper is also in the Hall of Fame.)
But the lesson is that if you believe history to be a barometer, all 72 players who made the weekend at Olympic Club are still in it.
The leaders are certainly strong. They have 16 major championships between them, although 14 belong to Woods.
He seems to be in control of his game in a way we haven't seen since the scandal. Woods has played the course brilliantly through two days, but it's by no means a lock that he will get his first major win since his epic playoff victory in this championship four years ago at Torrey Pines.
We all thought he was back after his win at the Arnold Palmer Invitational earlier this year. That was two weeks before the Masters and Woods tied for 40th.
You can't unconditionally trust that Woods will walk away with this title, which would be his fourth. Until his game holds up to major weekend pressure, it's fair to question Woods' chances to romp to victory.
Furyk and Toms aren't bums, either.
Furyk won this title in 2003 and Toms captured the PGA two years before that. Both fit the bill of a successful U.S. Open player. Neither is long, but both are straight. They are above-average putters and can move the ball easily.
As documented, no one is out of it.
Phil Mickelson, the record-holder for being a bridesmaid with five runner-up finishes, is eight back. Sounds like a lot until you think back to Janzen or Casper.
Lee Westwood, Ernie Els, Steve Stricker, Matt Kuchar and Jason Dufner are much closer to the top trio.
No player, no matter their pedigree or form, is immune from the potential danger that lurks on the hilly terrain of Olympic Club. No lead is safe here. No player is totally out of it.
At least that's what history has told us.