Rory McIlroy slipped to three shots off the lead at the Memorial Tournament at Muirfield Village as a stunning hole-in-one saw Steve Stricker take control.
The Ulsterman, who had shared the first-round lead with American Chris Riley, finished his second in Dublin, Ohio with the clubhouse lead after carding a level-par round to be six-under-par for the tournament.
However, Stricker came on strong and thanks to his later tee time stormed past the European Ryder Cup star to lead by three.
The hole-in-one was crucial for Stricker as a six-iron on the 188-yard eighth, having played the back nine first, found its way directly into the hole before a birdie on his last gave him a five-under round of 67.
The amazing finish saw him leap from a group of five sharing the lead to an outright advantage by three shots at the half-way point.
"It's a shock when you see that go in, obviously," Stricker, nine under overall on 135, said. "But in a good way! It was a great way to finish the round."
McIlroy, at 72 on Saturday, is level now with Ricky Barnes (70), Jonathan Byrd (67) and Australian Rod Pampling (66). The 22-year-old picked up three bogies in his front nine but managed to pull shots back with birdies coming on the second, fifth and seventh.
A good back nine, in which he carded a further three birdies, was damaged by a double-bogey on the par-four 14th and another bogey on the 18th.
"I felt as if I played good enough to shoot something in the 60s, but I just made too many mistakes out there," said the Northern Irishman.
Britain's new world number one Luke Donald is bubbling under the surface, five-under on 139 after a strong finish comprising successive birdies on his last two for a 69.