SANDWICH, England -- So flawless for so long, Louis Oosthuizen started making his worst swings of the week as his two-shot lead evaporated at The Open on Saturday.
With an hour left in a third round as undulating as the fairways at Royal St. George's, Oosthuizen found himself tied for the lead with Collin Morikawa and Jordan Spieth and facing a 10-foot par putt to avoid falling behind.
"I was a bit upset there," the South African said, "but got myself quickly together."
Oosthuizen delivered a key par save on the 15th and an 8-foot birdie on the par-3 16th. He finished with a 1-under 69, leaving him with a one-stroke lead and another good shot at ending his 11-year wait for a second major title.
"I will play my heart out tomorrow," the 2010 Open champion said, "and see if I can lift the Claret Jug again."
Saturday ended pretty much as it had started, with Oosthuizen, Morikawa and Spieth occupying the top three spots, three shots separating them.
Plenty happened in between.
Especially on the back nine and -- most tellingly -- on the 18th green, where Spieth missed a par putt from 2 feet for his second straight bogey to drop three shots back again.
It wasn't long before Morikawa and Oosthuizen, both one-time major winners some 10 years apart, were walking onto the green at the last. Oosthuizen's long putt over a hump from the right of green settled close to the hole for his par, then Morikawa slid a 12-foot birdie putt just past the hole.
Morikawa, the PGA champion last year and in his first links test, settled for a 68 and trimmed Oosthuizen's lead to one shot. He had been four shots behind after 10 holes and made a strong push at about the time Oosthuizen showed signs of fading.
"I don't have much experience on links golf, and pretty much all the highlights in my head are from this week," Morikawa said. "Thankfully there is quite a few. Hopefully we can just use that momentum from the first three days and just bring it into the last 18."
Oosthuizen, a runner-up in the past two majors, was at 12-under 198 and on course to be the first wire-to-wire winner at golf's oldest championship since Rory McIlroy in 2014.
The pin positions -- rather than the weather -- proved to be the greatest defense at Royal St. George's, with the wind not getting above 10 mph and a cloudless sky with bright sunshine looking sure to bring another day of low scoring.
However, pins were tucked away, sometimes near slopes, while the firmer fairways brought the deep rough and pot bunkers into play.
"Those are some of hardest pin locations collectively I've ever seen," said No. 2-ranked Jon Rahm, who shot 68 and is in contention, five shots off the lead.
A number of other big names were unable to launch a challenge.
Top-ranked Dustin Johnson started four shots off the lead but plunged out of contention by making five bogeys in his opening 11 holes. Two late birdies could give him only a 73, leaving him eight shots behind.
Brooks Koepka, a four-time major champion, was a shot further back after managing a round of 72.
McIlroy started much further back but reached the turn at 4 under for the championship after making five birdies. The back nine was another story, and McIlroy threw an iron to the ground -- he called it a "little toss" -- during a run of three bogeys in five holes on his way to shooting 69, his first round in the 60s at Royal St. George's. It left him at 1 under and with no chance of a second Claret Jug.
"The front nine was great. I keep saying I'm close, and that was sort of proof that it is in there," McIlroy said. "It's a matter of turning that nine holes into 18 holes and then hopefully turning 18 holes into an entire tournament. There are signs it is going in the right direction; I just couldn't keep it going for the rest of the round."
Instead, Corey Conners (66) and Scottie Scheffler (69) moved into contention at 8 under while Rahm -- looking to add The Open to his U.S. Open from last month -- was 7 under alongside Mackenzie Hughes and Dylan Frittelli.
Marcel Siem, who qualified from the second-tier Challenge Tour in Europe only last week, rebounded from an 8 after going out-of-bounds at the par-5 14th with two birdies in his final three holes. He was in a three-way tie for ninth place, six off the lead.
All of them are chasing Oosthuizen, who won the Open in 2010 and has rung up a career Grand Slam of runner-up finishes since then. That includes the U.S. Open last month, when he was leading with two holes to play until Rahm's birdie-birdie finish. He also was runner-up in the PGA Championship to Phil Mickelson.