Shane Lowry sits atop of the leaderboard at the Arnold Palmer Invitational after a superb 67, with Rory McIlroy four shots further back in a tie for fifth at the halfway stage.
Lowry was among the early starters and his five-under round around the Bay Hill course lifted him up to eight-under and into the clubhouse lead ahead of second placed Wyndham Clark whose 71 leaves him two shots back.
McIlroy, meanwhile, carded a 70 to sit in a tie for fifth on four under. He was joined on four under by Jason Day, who hit the round of the day with a 64.
Friday's action marks a stunning continuation of Lowry's turnaround in form at the Palmer family owned layout. Prior to his third placed finish last year, Lowry branded his record at Bay Hill as "horrific", with four missed cuts in his first four appearances and a modest tied-67th his strongest showing.
Lowry held a one-shot advantage over his compatriot at the start of play but their fortunes started to diverge on the second hole.
After McIlroy caught a clump of turf off the tee on the 233 yard par-three, coming up miles short of the green, Lowry hit a smooth four-iron into 30 feet.
With McIlroy unable to save par, Lowry fed his downhill birdie putt into the centre of the cup to draw within one stroke of overnight leader Clark.
The Irish pair both recorded birdies on the par-four third, McIlroy holing out from nine feet, with Lowry draining a seven-footer.
Lowry narrowly missed a chance to make it three birdies on the trot at the par-five fourth, while McIlroy fell victim to the dense greenside rough on the fifth, duffing his pitch and making bogey.
McIlroy did birdie the famous par-five sixth hole following a monstrous drive, though he flirted dangerously with the water after pulling his approach a tad left.
Lowry, meanwhile, struggled to make hay on the par-fives but was thriving on the shorter holes, sinking a 13-footer on the par-three seventh to tie the lead on six-under-par.
FULL LEADERBOARD
He then almost drifted out of bounds after a wild tee shot on the eighth but found a route to the green, pitching a low runner through the back, getting up and down well to scramble a par.
The 2019 Open champion took sole possession of the lead for the first time around the turn, draining a five-footer at the short-ish par-four 10th.
Tied with Clark on seven-under, Lowry made a big move on the 13th, which had yielded just four birdies all day until that point.
From the heart of the fairway, Lowry winced at his approach, which was pulled to the left side of the green but then he proceeded to roll in a 35-foot putt to re-take the outright lead on eight-under.
With birdies infectious, McIlroy followed him in with a birdie putt almost as long to get to three-under-par.
Lowry holed a 10-foot par save on the par-three 14th after a misjudged tee shot and a tentative lag putt.
Things took a turn for the chaotic late on. Lowry's strangely abject form on the par-5s as he registered his first bogey of the day on statistically the course's easiest hole, the 16th. A wild drive forced a lay-up but he still should have been able to rescue at least a par, except for a missed six-footer.
However, his ownership of the lead was restored as Clark was simultaneously in the process of double-bogeying 15, having driven out of bounds. Even more bizarre, the 2023 US Open champion - in stunning putting form - sunk another lengthy putt to avoid a triple.
While this was ongoing, McIlroy recorded a cool birdie on the par-5 16th and was back to within three of Lowry's lead.
He inched even closer on 17, sinking a 33-foot birdie from the front of the green to climb to five-under and a tie for third. However, he would give that back on the last after pushing his drive right. The resulting bogey saw McIlroy reach the midway point on four-under par after a second successive 70.
His playing partner Lowry would finish with a flourish to head the leaderboard by the close of his round. The Clara golfer sealed a marvellous putting display - marred only by the howler on 16 - by holing a left-to-right breaking birdie putt from the fringe to reach eight-under thru 36 holes.
