Francesco Molinari produced a barrage of birdies on the back nine to take control of The Masters as Tiger Woods remained firmly in contention after a high-quality third day.
Molinari surged into the outright lead with four consecutive birdies from the 12th and went on to complete a bogey-free 66 to close on 13 under par, two shots clear of Woods and Tony Finau as the tournament faces a race against time to beat the weather on the final day.
Due to the threat of afternoon thunderstorms, the Augusta National officials took the rare step of bringing forward Sunday's tee times and ultilising a two-tee start for the first time since 2005, with the players going out in threeballs and the final group starting at 2:20pm (BST).
The committee are confident of being able to slip a Green Jacket on the champion before the adverse weather arrives, and Molinari put himself in prime position to double his major collection having completed 54 holes with just a single bogey on his card - at the 11th in the first round.
The Italian's swing was metronomic throughout the day, and he backed up his consistency from tee to green with the kind of assured putting that earned him a memorable Open triumph at Carnoustie last July, when he upstaged playing-partner Woods in the final round.
Molinari holed a couple of clutch putts in his five opening pars before picking up shots at the sixth and eighth as he cruised to the turn in 34, and he came close to a rare ace at the 12th to set up the birdie that ignited his charge to the top of the leaderboard.
The 36-year-old then found the heart of the 13th green in two and two-putted for birdie, knocked another sweet iron in close and converted the birdie putt at 14, and he did well to get up and down from just off the back edge of the 15th green for his sixth red number of the day.
Molinari safely negotiated the final two holes in par - thanks to a deft sand-save from long distance at 18 - to remain on 13 under, and he can look forward to another major final round alongside fan-favourite Woods, with Tony Finau completing the final group of the 83rd Masters.
Finau started the round four off the lead but got off to the ideal start with birdies at the opening three holes and, after another gain at the sixth, his second to the long eighth pulled up two feet short of dropping for an albatross and leaving him with a tap-in for eagle.
After scorching to the turn in 30, Finau threatened to at least match the course record when he birdied the two par-fives on the homeward stretch, but he was unable to find another as he settled for a 64 and the early clubhouse lead on 11 under.
He was later joined by four-time champion Woods, who looked a little out of sorts early in his round and followed four pars with a dropped shot at the fifth to raise fears that he would head in the wrong direction on moving day.
But his response was immediate and thrilling as he wowed the patrons with three straight birdies while producing a couple of trademark scrambled pars to atone for the odd, errant drive into the pines.
Woods missed a great chance to advance further on the 12th, and his pulled drive at 13 took a fortunate kick off the branches and back into play, which he took full advantage of with a birdie four before a neat up-and-down at 15 got him to 10 under.
A bold tee shot at the 16th resulted in his sixth birdie of the day, and he parred in to stay in a share of second which ensured him his place in Sunday's final threesome with Molinari and his Ryder Cup team-mate Finau.
Brooks Koepka's hopes of a third major win from the last four remained intact, although he will strive for more consistency over the final 18 holes after carding a mixed-bag of a 69 which featured an eagle at 15, five birdies but also four dropped shots which leave him three off the pace on 10 under par.
The reigning US Open and PGA champion is alone in fourth and one shot ahead of Ian Poulter, who matched his opening-day 68, while Webb Simpson roared into the mix with a classy 64 having been six shots off the lead at the halfway stage.
Poulter struggled to make much happen as he began with seven straight pars with playing-partner Woods garnering most of the attention in their group, but the Englishman suddenly came to life with back-to-back birdies to close out the front nine.
He responded to a bogey at 11 with birdies at each of the par-fives on the inward half, and he finished in style with a pin-high approach to the final green which he converted for his fifth birdie of the round to close on nine under par.
World No 2 Dustin Johnson bogeyed the last to return a 70 and slip into the group on eight under which also includes Matt Kuchar (68), Justin Harding (70), Louis Oosthuizen (71) and Xander Shauffele, who got to 10 under before finding water with his second to 15 while also dropping a shot at the last in a disappointing finish to his 70.
But one of the star names out of contention is Rory McIlroy, who was again left to count the cost of "too many mistakes" as he took his bogey tally for the week to 14 in a 72 which sees him go into the final round 12 shots off the pace on one under par.
Final round coverage will now begin at 1pm (BST) on Sky Sports Golf, with full live coverage starting at 2pm.