Rory McIlroy quickly took over the lead from Sergio Garcia when the final pair belatedly began their closing rounds in the WGC-Bridgestone Invitational.
Torrential rain which forced play to be suspended earlier in the day meant The Ryder Cup team-mates did not tee off until 3:20pm local time at Firestone Country Club, 75 minutes later than scheduled.
But McIlroy wasted no time in overhauling a three shot deficit with birdies on the first three holes as he sought the victory which could see him reclaim the World Number One spot for the first time since March 2013.
The Open Champion pulled his opening drive into the rough but had a gap through the trees and hit a superb low pitch to three feet, while Garcia had to settle for a par by two-putting from long range.
McIlroy then two-putted from long range on the par five second for another birdie as Garcia missed from six feet.
McIlroy also birdied the third to take over the lead as Garcia bogeyed, but that did not tell half the story of an amazing hole.
Garcia's errant drive into the crowd somehow knocked the diamond out of a female spectator's engagement ring and after giving her a signed ball, Garcia asked for her contact information after hitting his second shot over the green.
Thankfully the precious stone was quickly recovered but Garcia was unable to get up and down to save par and McIlroy holed from eight feet for a third straight birdie.
There was already plenty of evidence that the rain-softened course was vulnerable to low scoring.
Five-time Major winner Phil Mickelson had charged through the field with an eight under par 62 which featured ten birdies and two bogeys, the left-hander having been disgusted with his opening three rounds.
"I don't know what to say, it kind of came out of nowhere," Mickelson said after finishing five under for the tournament. "The first two rounds really threw me for a loop. I have been struggling getting my short irons close and today they were right on.
"I made a lot of birdies and it was nice. Today was a big day to give me a lot of confidence and momentum heading into the US PGA next week."
England's Lee Westwood had also found some welcome form after four consecutive missed cuts, the 41 year old carding a flawless 63 that did not go unnoticed by watching Ryder Cup Captain Paul McGinley.
"If you look at the one pillar that has been consistent throughout the Ryder Cup success we have had since the 90s it has been Lee Westwood but you want to see Lee in form," McGinley said on Sky Sports.
"He is not going to get in on his reputation alone. He needs some form, he knows that and it's good to see him playing well today."
When McIlroy also birdied the fifth from five feet it meant a five shot swing had taken place in the space of five holes and gave the World Number Two a two shot lead.
Garcia desperately needed something to go in his favour and it happened on the eighth, McIlroy driving into the rough and finding a greenside bunker with his approach, from where he failed to get up and down.
Garcia, who had won just three times on the 15 occasions he held the lead after 54 holes, then got back on level terms with a birdie from 15 feet on the ninth, McIlroy missing from just six feet.
That meant the pair went into the back nine tied on 14 under par, a back nine Garcia played in just 27 shots in his second round of 61 on Friday.
