Sergio Garcia, tuning up for his Masters title defence at Augusta National, rallied from 2 down through 11 holes to beat rising US star Xander Schauffele
Defending champion Johnson, who suffered an upset loss to Bernd Wiesberger on Wednesday, was beaten 4&3 by Canada's Adam Hadwin
Four-time major winner McIlroy has moved up six places to seventh in the rankings
Four-time major champion McIlroy outdueled American Bryson DeChambeau and major winners Tiger Woods, Justin Rose and Henrik Stenson
Park, a seven-time major winner, opened with four birdies and an eagle in the first five holes and vaulted atop the leaderboard at 14-under 202.
Sweden's Stenson, the 2016 British Open champion, fired a one-under par 71 to stand on 12-under 204 after 54 holes at Bay Hill
The 2016 British Open champion stand alongside American Bryson DeChambeau on 11-under 133 after 36 holes while Tiger Woods slipped
Sweden's Henrik Stenson made nine birdies against a lone bogey to open with a 64
The alterations, such as allowing the flag to remain in the hole unattended while putting, come into force on January 1.
14-time major champion Woods showed he's a contender again as he fired a one-under-par 70 to share second on nine-under 275
Woods, the 14-time major champion playing his fourth Tour event since spinal fusion surgery last April ended a brief comeback bid in 2017, is seeking his first title since 2013.
Woods was the center of attention, and after years of battling injury he gave his fans what they wanted to see.
A strong comeback on the final day helped Asia-Pacific win their first trophy since 2004
The 21-year-old shares the lead with England's Matt Wallace on seven-under 209
Europe stage strong comeback to take a two-point into the final day in Bonallack Trophy