Jason Day will take a two-shot lead into the weekend of the Arnold Palmer Invitational as Henrik Stenson and Justin Rose surged into contention on day two at Bay Hill.
Day made the most of perfect scoring conditions early on as he fired a flawless 65 to claim the early clubhouse lead on 13 under, and he enjoyed a five-stroke advantage as the later starters hit the course.
But Stenson trimmed Day's lead to two as he covered the inward nine in just 31 to return a superb 66, a score matched by Rose in the group behind as the Englishman went bogey-free.
Rory McIlroy avoided a weekend off as he bounced back from his opening 75 with an encouraging 67 which lifted him to two under, although he has 11 shots to make up on the leader.
Day started at the 10th and followed a pair of pars with a neat pitch to inside three feet at the long 12th to set up his first birdie of the round, and he added another at 16 after narrowly missing an 18-foot putt for eagle.
Day then rolled in a huge 35-footer for birdie at the 17th, and he picked up another shot at the third, where his 91-yard approach almost spun into the cup for an eagle-two.
The world No 2 carded another birdie at five and he got up and down from a greenside bunker for another gain at the next, and he capped a superb day's work in thrilling style as he drained another birdie putt from just inside 40 feet on the ninth green.
"It was great. I felt like I couldn't do anything wrong out there," said Day, whose halfway score was just one outside the tournament 36-hole record. "I was driving it nice and driving it really long. I had several shots to hit a lot of greens and I putted fantastic.
"To hole 125 feet of putts was fantastic and the putts on nine and 17 definitely helped that along. But I was very, very pleased. My goal was to try and stay patient but still aggressive and it worked out over the last two days."
Stenson emerged as Day's closest challenger as the Swede recovered from an early blemish at the second with birdies at the sixth and eighth, and he also birdied every other hole on the back nine - closing in style with a 20-foot putt for a three at the tough 18th.
Rose opened with three pars before getting up and running with three consecutive birdies from the fourth, and excellent pitched to the 10th and 12th set up further gains for the world No 8.
He two-putted for his sixth birdie of the round at the long 16th and parred safely in to close on 10 under, while his compatriot Paul Casey is three shots further back as he continued his encouraging recent form with a 69, although he took the gloss off an excellent inward nine with a bogey at the last.
The Englishman dropped a shot at the first after pulling his drive into the rough on the left, but he responded with a 15-foot putt for birdie at the third before getting up and down for another at the long fourth.
Casey took another step back at the ninth when he missed a four-footer for par after bunkering his approach, but he reeled off three birdies in four holes after the turn and two-putted from distance for another at 16.
But a blocked drive and a pulled second cost him a shot at the last as he slipped to seven under, while South Korean veteran KJ Choi (70), Jason Kokrak (68) and David Hearn (67) were all a shot further adrift in the clubhouse.
But Matt Every, champion for the last two years at Bay Hill, will not make it a three-peat as he missed the cut after a disappointing 74 which included a triple-bogey seven at the 11th - his second hole of the day.
Every finished on one over, a shot outside the cut mark, while Luke Donald will also have the weekend off after an erratic 75, closing with a double-bogey six at the last when he put his second shot into water.
Meanwhile, Saturday's third round will start much earlier than scheduled due to the threat of electrical storms that are forecast to hit the Orlando area in the evening. The players will go out in three-balls in a two-tee start, with Day, Stenson and Rose teeing off at 1:30pm GMT.
Live coverage of the third day at Bay Hill will now begin at 1pm on Sky Sports 4 - your home of golf.