Australian Jason Day has moved within two strokes of leader Rory McIlroy with a magnificent eight-under 64, just one stroke shy of matching the course record at Augusta National.
Nine months after McIlroy followed an opening 63 at the British Open with a horrific 80 at blustery St Andrews, the 21-year-old from Northern Ireland made a solid statement after a 65 had made him the youngest 18-hole Masters leader.
McIlroy stood on 10-under 134 after 36 holes while 23-year-old Australian Day, in his first Masters, shot a stunning eight-under 64.
Day's bogey-free round saw birdies at the second and par-four seventh and ninth then closed with five birdies in eight holes, the final one a tap-in at 18.
"I watched Rory do it yesterday and he looked like he had done it pretty easily," Day said.
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"I can't even remember shooting 8-under out there. It was just a bunch of fun.
"I'm looking forward to the weekend. I'm going to be nervous obviously. I'm going to try to go out there and relax and have fun no matter what happens."
The two will play together for the third day in a row in Saturday's final group.
"I played the front nine really nicely and we just fed off one another," McIlroy said.
"We've shown we're comfortable playing out there with each other. We had a lot of fun. I'm really looking forward to the weekend."
McIlroy could become the second-youngest winner in Masters history, a few months older than Tiger Woods when he won in 1997, and the first European champion at Augusta National since Spaniard Jose Maria Olazabal in 1999.
Playing in only his ninth major, the Ulsterman has three third-place major finishes - the 2009 and 2010 PGA Championships and last year's British Open.
McIlroy birdied the par-five second after chipping inches from the cup, moved ahead after a bogey by Choi and took command with birdie at the par-four fifth. He reached 10-under par by sinking a five-foot birdie putt at the ninth.
But he stumbled at the par-three 12th, finding the front bunker off the tee over Rae's Creek and missing a 10 foot par putt for his first bogey of the event, becoming the last man in the field of 99 to suffer one.
McIlroy answered quickly. He blasted a 310.9 metre tee shot and dropped a 164.59 metres approach shot 12 feet from the pin, setting up a tap-in birdie, and parred in from there.
South Korean KJ Choi fired a 70 to stand third on 137, one stroke ahead of Australian Geoff Ogilvy, who shot a 69, and Spain's Alvaro Quiros, who shared the first-day lead with McIlroy but slipped to a 73 on Friday.
World No.7 Woods, a 14-time major champion chasing the record 18 majors won by Jack Nicklaus, was five-under for the day and six-under for the tournament after making his sixth birdie in eight holes on the par-5 15th.
Woods, mired in a win drought of nearly 18 months, opened bogey-birdie-bogey and squandered a birdie at six with a bogey at seven before starting his run.
Day or Ogilvy could give Australia it's first champion in the only major no Aussie has ever won.
Quiros, the long-drive leader, opened with a bogey but finished the front nine at par. He missed eight-foot putts for birdie at 11 and bogey at 12 but a closing birdie brought new hope.
Fred Couples, the 1992 Masters winner who could become the oldest major champion in history at age 51, fired a 68 to share sixth on 139 with fellow Americans Rickie Fowler and Ricky Barnes and South Korean Yang Yong-Eun.
Level with them at five-under through 17 was England's second-ranked Lee Westwood, last year's Masters runner-up.
A victory this week would put Couples past the oldest current major winner, Julis Boros at 48 at the 1968 PGA Championship, and the Masters age mark of 46 set by Nicklaus in his epic triumph 25 years ago.
Defending champion Phil Mickelson fired a par 72 to stand on 142.
World No.1 Martin Kaymer of Germany was set to miss the cut for the fourth time in as many Masters starts.
