Peter Hanson produced the low round of the week to take a one-shot lead heading into the final round of the Masters.
The Swede shot a superb seven-under-par 65 at Augusta National to finish on nine under par and lead by one over Phil Mickelson, who himself shot a six-under-par 66 to set up a great chance of securing a fourth green jacket.
South African Louis Oosthuizen follows a shot behind the American after a 69, while Bubba Watson produced a two-under 70 to finish alone in fourth place a further shot back.
Padraig Harrington (68), Lee Westwood (72), Hunter Mahan (68) and Henrik Stenson (70) are tied for fifth on four under, five shots off the lead.
The day belonged to Hanson, however, who missed the cut on his only previous visit to Augusta last year but looked very much at home on Saturday.
After bogeying the first hole to drop back to one under, Hanson found his touch, making eight birdies in all - including four in his final five holes alone to rocket into the sole lead.
"It felt great," said the 34-year-old. "After bogeying the first it was important I made up ground straight away with a birdie on the second.
"Then I just tried to hang on in there - the back nine was pretty smooth.
Hanson will partner Phil Mickelson in Sunday's final pairing for the third time this week, the two having played the first two rounds in the same group along with Hunter Mahan.
"I learnt a lot from Phil and I hope we can play together on Sunday - he's a great guy," he added.
"But for now I'm just going to enjoy the moment."
A number of big names fell out of contention after their third rounds, including Tiger Woods (72) and Rory McIlroy (77), who find themselves 12 and 10 shots back respectively.
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