Lee Westwood tossed away the Masters lead with a closing double bogey at Augusta - as Rory McIlroy came right back into the thick of things.
England's world number three, ahead by one after an opening 67, still held that advantage until he missed the 18th green, chipped ten feet past and ran up a six.
A one-over-par 73 dropped the 2010 runner-up to four under for the opening major of the season and left Americans Fred Couples - champion 20 years ago and now 52 - and Jason Dufner out in front on five under.
McIlroy reached the same mark before failing to get up and down from a bunker at the 17th, but then saved par from off the final green and with a fine 69 joined Westwood and Spanish star Sergio Garcia only one behind.
And that, of course, after he began with a double-bogey six yesterday on his return to the course where he led by four with a round to go last April, then crashed to an 80.
Westwood said: "It was a disappointing way to finish, but if you get out of position on this course it can punish you.
"These things happen and they will happen to everybody."
Henrik Stenson was leading when he took eight on the hole on Thursday.
"I thought I made a few putts that didn't drop," added Westwood. "But I'm right in there for the weekend and that's where I want to be.
"The greens are getting more fiery and the wind is making it tricky."
McIlroy had finished his opening 71 with back-to-back birdies and said: "That was huge and it was nice just to get up today and get straight back at it.
"It put me in a positive frame of mind. I know I am playing well - my recent results (only one finish outside the top five since last August) show that.
"I just wanted to come and play and put myself in position to win another tournament, another major."
Two months after his Masters meltdown a year ago, he won the US open by eight shots.
Couples, captain of the American Presidents Cup team last November, described it as "a little bizarre" to find himself out in front after a "magical" 67.
But it was not totally surprising. He has finished sixth and 15th the last two years and stated: "It's my favourite place in the world to play.
"On the range I felt my body tightening up a bit and I just wanted to play solid."
Phil Mickelson and Tiger Woods, with seven green jackets between them, were not out of it.
Mickelson had been four over after a triple-bogey seven at the tenth on Thursday, but he followed up his 74 with a 68 to be two under and despite the 18th playing so tough into the wind he birdied it from 18 feet.
Woods was among the later starters and birdied the first and third to get to two under as well, but then bogeyed the fourth and sixth.
At level par he was still in a lot better position than world number one Luke Donald, who in the final group of the day was five over after a double-bogey seven at the eighth.
He could not afford to drop another shot if he was to survive the halfway cut.
Ian Poulter reached two under, but he went in the water for a double bogey at the short 16th and remained level par with a second successive 72.
Poulter said: "I'm a little bit disappointed - it obviously leaves a little sour taste."