Justin Rose fired a second-straight 66 on Friday to claim a share of the halfway lead alongside Tom Gillis at the US PGA Tour Honda Classic.
Gillis carded a 64 to join Rose on eight-under 132, one shot in front of red-hot Rory McIlroy of Northern Ireland.
McIlroy, who could claim the world number one ranking with a victory this week, had four birdies in a three-under 67 at PGA National.
"I had a few chances early on and didn't take them," McIlroy said. "Kept making pars and making pars, and broke that run with a bogey on 13 which was frustrating.
"But to bounce back from that and birdie three of the last five holes was nice, and puts me in great position going into the weekend."
McIlroy said he wouldn't change his approach on the weekend, even with the prospect of supplanting Luke Donald atop the rankings hovering.
"I just need to keep doing the same things, try to drive the ball in the fairway and give myself loads of opportunities, and try and take a few," he said.
"Because you don't need to make tons of birdies out here."
Plenty of birdies were being made, however, including eight for unheralded Brian Harman, who also had an eagle as he flirted with the golf grail of 59 before settling for a course-record 61 with a par on 18.
Tiger Woods capped a scrambling round with back-to-back birdies that gave him a two-under 68.
That put him at one-under 139 for the tournament, still seven off the pace.
The 14-time major champion had his struggles, including a tee shot that found the water leading to a double-bogey on the par-three fifth.
Rose, who teed off on 10, had five birdies in a nine-hole span in the middle of his round, moving as low as 10-under until bogeys at the sixth and seventh slowed him down.
"You can't play 36 holes around here and expect to come away without any bruises at all," Rose said.
McIlroy was joined on seven-under 133 by Dicky Pride, who birdied his final hole to complete a 67.
Harman headed a group on 134 that also included Jimmy Walker (67) and Monday qualifier Vaughn Taylor (66).
Harman, a US tour rookie, was in the fairway at the par-five 18th needing an eagle to post a 59.
He fired into the front bunker, then missed a five-foot birdie putt. His 61, however, lowered the course record by three strokes.
"Just one of those crazy days where everything comes together," Harman said. "Got off to a really hot start and just kept the pedal down all day. It was awesome."