Scotland's Martin Laird tumbled out of the lead just as world number one Rory McIlroy was crashing out of golf's richest event again on Friday.
Joint overnight leader with Ian Poulter - one of the late starters in the second round of the Players Championship at Sawgrass - Laird made further good progress until he came to the famed closing stretch.
The Glaswegian found the water with his second shot to the long 16th and then hit a shocking tee shot on the short 17th to find the same lake.
They cost him a bogey six and a double bogey five and the sad finish was complete when he left a chip well short on the last and bogeyed again.
It meant a one over par 73 to go with his brilliant opening 65 and, having fallen from 10 under par to six under, he was suddenly two behind new pacesetter Zach Johnson, round in 66 even with a closing bogey.
McIlroy, who two years ago revealed his dislike of the Pete Dye-designed lay-out, was resigned to missing the halfway cut for the third successive time in the £5.8million tournament after a 76 left him four over.
The 23-year-old, expecting so much more of himself this time after being in a play-off at Quail Hollow last Sunday, started his round with a 17-foot birdie putt.
But that was as good as things got. He bogeyed the short 13th, had to settle for par on the 16th after also going in the drink and then dropped further strokes at the 18th, first and fourth.
His exit opened the door to Luke Donald and Lee Westwood to take over the number one spot again and both head into the weekend on three under.
Whether Tiger Woods was in the field with them remained to be seen. He resumed just after Poulter on two over.
Laird said: "That's what this course will do to you. I got a bit greedy with a four-iron to the 16th - it was a stupid shot - and was between clubs at the 17th.
"A nine-iron was too much and a wedge not enough, but I didn't hit it real solid and the wind got it. It was a bad shot.
"But as big a car crash as I just had I'm still well in it. I'd have taken my position before the start."
Donald eagled the 16th and second, first hitting a five-iron to six feet and then making a 20-footer, but then undid some of his good work before a closing birdie on the ninth.
"It could have been a special round," he said. "I threw in a couple of bad swings, but 69 is not a bad score.
"I am quietly optimistic. I think this course is only to get tougher and eight or nine under could be a good score come Sunday."
Westwood, who also birdied the ninth for a 70, said: "I didn't play as well as yesterday, but shot one better - that's golf.
"I'm playing all right. I like this course and it suits me.
"I suppose three under is in touch. Hopefully it will firm up and the greens will get quicker."
Laird and Poulter were not the only British golfers high up the leaderboard. London's Brian Davis, based in the States like Laird, was six under playing the last.
But McIlroy's fellow Irishman Graeme McDowell, who led by three late in the third round last year, was in danger of missing by one on one over.
As Poulter and Harrington - three under teeing off again - set off with double bogey sixes McIlroy made hasty plans to fly straight back home.
"There's something about this course I can't quite get to grips with," he said. "It's disappointing - I'm not going to lie.
"I've been playing well for the last 12 months. This is my first missed cut for a year.
"I'll get ready now for the big tournaments coming up."
Next is the BMW PGA Championship at Wentworth in a fortnight and his US Open defence is little more than a month away.
He vowed to return next May to try again - last year he skipped the event - but said: "I'm a visual player and I struggle to see the tee shots required here."
Davis bogeyed the last like so many before him, but was in a tie for second place two behind Johnson.
Poulter, who had missed the green and three-putted on the 10th, pulled his tee shot into the water on the 13th and double-bogeyed again to be five behind Johnson.
With the wind picking up, the cut was moving towards one over - and that was where Woods moved to with a six-foot birdie putt on the fourth after three opening pars.
He was up from 100th overnight to 77th, with the top 70 and ties going through at the end of the day.
Poulter managed only 40 for the back nine and had fallen to joint 18th alongside Donald and Westwood.
Woods gave a shot back on the fifth, but produced a superlative birdie at the fiendishly difficult 237-yard eighth, hitting his tee shot to 10 feet.
He was in a greenside bunker for two at the downwind long ninth, splashed out to six feet and made it for a second successive birdie.
Out in 34 he was inside the cut mark at level par, but still had nine to play.
Harrington, meanwhile, was one under with seven to go and had some tough holes to come on the front nine.
