Chris DiMarco has a four-shot lead over a star-studded chasing pack after an eventful three days at the Masters.
The 36-year-old started the day on five under having played one hole of his second round, and he ended it on 13 under having played nine of his third.
His 67-67 start gave him a four-shot lead after 36 holes, and three more birdies on the front nine of his third round maintained that lead.
Leading the chase behind DiMarco was Tiger Woods, who was 11 under par.
The 29-year-old American, who started Saturday on two over par after 19 holes completed, carded a six-under 66 in his second round - the best so far this week - and then raced to the turn in his third round in just 31 shots.
The three-times Masters champion had just tapped in for his third straight birdie when the hooter sounded to end play for the day at Augusta.
"The course was not playing as difficult as it normally does," said the world number two.
"You could feed the ball into the flags and be aggressive. Everybody was aggressive."
One shot behind Woods is Denmark's Thomas Bjorn, who stormed into contention with a five-under 67 in the second round that included two eagles and a birdie-birdie finish.
DiMarco, who recorded three top-10 finishes in the majors last year, was six shots clear of the field before Bjorn's late flurry.
The Dane's intervention prevented DiMarco from setting a new record for a 36-hole lead at the Masters.
The US Ryder Cup man, who played in the final group at Augusta last year, has now led after a round at the Masters five times in five years. His best finish remains the tie for sixth he managed in 2004.
But the Florida-based DiMarco is convinced he can learn from that experience.
"I watched how to win," he said. "I had the best seat in the house and what I saw was that Phil had fun.
"He also played some very good golf and was aggressive."
Woods played 26 holes on Saturday in a brilliant 11 under par
The leader also saw an advantage in the fact that he had 27 holes to play on Sunday, not the usual 18.
"This way I won't have to sit around all morning and wait for seven hours to play."
Four shots behind Bjorn, and nine behind DiMarco, on four under par are Australian duo Rod Pampling and Mark Hensby and world number one Vijay Singh.
There are then six players tied on three under, among them defending champion Phil Mickelson and England's joint overnight leader Luke Donald.
The European Ryder Cup star fell away with a second-round 77, but was then four under for the 15 holes of his third round he managed before the light went.
Donald's Ryder Cup team-mate and compatriot David Howell had also started the day alongside DiMarco on five under, but two late bogeys in his second round and a double-bogey start to his third saw his slide out of contention.
The 29-year-old Howell, who was paired with Woods, did settle down, however, and birdies at the seventh and eighth got him back to two under alongside another European Ryder Cup player Thomas Levet, US counterpart Chad Campbell and Australian Craig Parry.
Campbell, in fact, can claim the third-round clubhouse lead as he managed to finish his third round before the light failed.
The only two other players under par at the close of play were Adam Scott and Jim Furyk.