Viktor Hovland stormed into a two-shot halfway lead at the Arnold Palmer Invitational, as Rory McIlroy was left to rue a costly finish to his second round.
Hovland, chasing a fourth victory in his last eight worldwide starts, mixed seven birdies with a lone bogey to card a round-of-the-day 66 at Bay Hill and jump to nine under.
The world No 9 moved into the solo advantage when overnight leader McIlroy bogeyed two of his last four holes to close a level-par 72, seeing the Northern Irishman drop back tied-second alongside Tyrrell Hatton and Talor Gooch.
- Arnold Palmer Invitational: Latest leaderboard
- WATCH: Nick Watney splashes shot through water!
- When is the PGA Tour live on Sky Sports?
"I'm not particularly happy with how I hit the golf ball, certainly the last few days," Hatton said. "I think the score is pretty flattering. I've putted really good, which is why I've got the score that I have, but I know that I can't keep hitting it that badly certainly with it going to be playing much tougher this weekend."
Beginning on the back nine, Hovland holed from 20 feet at the 10th and took advantage of the par-five 12th, before bouncing back from a bogey at the 13th to make three consecutive birdies from the 15th.
Hovland picked up shots at the par-five fourth and sixth to set the clubhouse target, with Hatton his closest challenger after the morning wave when he birdied three of his last five holes to card a second-round 68.
McIlroy, looking to build on Thursday's seven-under 65, responded to bogeying his opening hole by making a two-putt gain at the par-five fourth, adding another birdie at the seventh and holing a 45-footer from the fringe at the eighth.
The four-time major champion lost his share of the lead when he three-putted from 30 feet at the par-four 15th, before missing an eight-foot birdie chance at the par-five next and then failing to convert from the same distance to save par on his penultimate hole.
Billy Horschel sits three shots off the lead in fifth spot, while Scotland's Martin Laird and England's Paul Casey are in the group of seven players six strokes back in a share of sixth place.
World No 1 Jon Rahm posted a two-under 70 to sit eight behind going into the weekend, while Masters champion Hideki Matsuyama is tied-39th after rounds of 73 and 72.
Watch the Arnold Palmer Invitational throughout the weekend live on Sky Sports. Live coverage continues Saturday from 2pm on Sky Sports Golf, ahead of full coverage from 5.30pm.