Sergio Garcia continued his serene progress on a turbulent day at the Deutsche Bank Championship as a six-under-par 65 put him two strokes clear heading into the final round.
The Spaniard has been in indifferent form of late but has been consistently excellent at TPC Boston, his 19-under total from rounds of 65, 64 and 65 putting him two clear of Sweden's Henrik Stenson.
A bogey at the par-four 14th - the same hole at which he had a double on Saturday - proved to be the only blemish for the Spaniard as he sunk seven birdies on a day of low scoring, after thunderstorms in Massachusetts forced a restart of third round but ultimately left soft conditions for the players to work with.
Canada's Graham DeLaet and Steve Stricker carded rounds of nine and eight under respectively to sit 16 under in joint third, while lower down the leaderboard there were signs of a return to form for Rory McIlroy.
The former world number one had by far his best day of the tournament as his seven-under 64 put him into a share of 29th on eight under overall. Graeme McDowell posted a 69 to lie on six under.
Tournament officials announced they would be sending the players out early in threesomes, starting from the first and 10th tees, in a bid to beat the weather.
On Sunday, around an hour's play was erased when officials decided to start the round over because of thunder and lightning.
The delay meant the course was in near darkness by the time Garcia birdied the 18th to confirm his two-stroke lead.
Garcia does not have a win to his name this season and has endured a particularly alarming dip of form recently.
He performed poorly at the World Golf Championships-Bridgestone Invitational and the PGA Championship and has not had a top-10 finish since May.
His nerve will be tested on the final day as a high-quality field chases him and Stenson, who also birdied 18 on Sunday. DeLaet bogeyed the first but was flawless from there as 10 birdies gave him a career-low 62, while Stricker's 63 was highlighted by an eagle on the par-five 18th.
"It was an incredible day," DeLaet told pgatour.com. "It's one of those days that it doesn't come along as often as you'd like."
Behind them were US PGA champion Jason Dufner and Roberto Castro on 15 under, Kevin Stadler on 14 under and Ian Poulter on 13 under.
One player who did not find conditions to his liking was Tiger Woods. The world number one was one of a handful of players to finish over par for the day with a 72. He said: "The course is gettable, that's for sure.
"You could be very aggressive and not have to worry about anything. Just one of those days I had a bad day at the wrong time."