Then came No. 5.
Oosthuizen hit a snap hook off the tee that left him reaching for his right shoulder as the ball dove into the woods and landed in the middle of shoulder-high bushes. He had no option but to take a penalty drop out of the hazard, then laid up short of the creek and two-putted for double bogey.
McIlroy's tee shot found a clump of native grass on the edge of a bunker, and he had to chip out short of the creek to make bogey.
They were tied.
But Oosthuizen was hurting. He couldn't get through his swing on the next tee shot, which sailed into the bunker. He said adrenaline helped him forget about the pain.
But it was too late.
McIlroy went right at the sixth flag, hitting 9-iron into 3 feet for birdie and a lead that he never gave back.
"It was a great bonus after making bogey at the fifth to bounce straight back with that birdie," McIlroy said. "Once I got into the lead, I felt very comfortable. ... It worked for the most part. Obviously had a couple wobbles there coming in, but did enough in the early part of the round to have enough of a cushion to get the job done."
Woods lurked until the end — he had a 23-foot eagle putt on 18 that would have put him within a stroke of the leaders — but it was really a two-man race until Oosthuizen missed from just inside 10 feet for par on the 17th and from 12 feet on the 18th.
"I probably made all my putts yesterday," Oosthuizen said.
The drama wasn't only at the top of the leaderboard, though: Charlie Hoffman was trying to salvage a spot in the top 70 in the FedEx Cup standings to advance to the third playoff event next week in Indianapolis.
Hoffman, who won here two years ago, was 13 under after a birdie on the eighth hole before playing his next nine in 8-over par — including a quadruple-bogey 7 on the par-3 11th. He came to the 18th needing a par to advance.
Hoffman went over the green in two, barely chipped on and then ran his putt 12 feet past the hole.
He made the putt for par.
"I didn't expect to be playing next week," Hoffman said. "Shooting 42 on the back nine, I don't think I deserved to play next week. But I guess I've got another chance."
Others who advanced included Dicky Pride, who birdied his last two holes to get the 70th spot by one stroke over Jonas Blixt; and Chris Kirk, who stumbled at the start only to birdie four of his last five holes.
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