"Didn't miss many shots out there", Rahm said. "It's sort of position and irons of the tee and really trying to plot your way around the golf course". The only bogey today I made was at the 6th and it was after a good shot that landed a foot from the hole.
There were too many to single out for the 24-year-old Spaniard, who was at 15-under 201. But you can also get it the other way, as soon as you start struggling and start going the other way, it can easily go against you.
McIlroy opened bogey-bogey, settled down with four birdies but then hit a dry spell of pars down the stretch.
Rahm's inward 30, which included a close-call for an albatross at the 11th, capped an eight-under 64 which swept him into the outright lead ahead of his Ryder Cup team-mates, who recovered from nervy starts to post creditable 70s in cooler, softer conditions for day three at TPC Sawgrass.
On Friday, just when it looked as if Fleetwood would take a three-shot lead into the weekend, McIlroy eagled No. 16 and birdied 17 to climb into a tie at the top. Even on the par-5 16th, he tried a low runner out of the pine trees and it came out so hot that it ran through the green and into the water.
"I was hitting my irons very, very well", Rahm said.
"I felt like I could have got something in the 60s today and got off to not actually the best of starts today, " Woods said.
McIlroy, meanwhile, signed for a 70 after a slow start saw him drop shots on the opening two holes. He holed a 30-foot birdie putt on No. 8 after McIlroy tapped in for his birdie, and then picked up four birdies where they were available for his 70.
"It was just a grind", he said.
"It was a real test of grit and mental strength. Under par is always a good score around here no matter how you play".
They shared the lead at 12-under 132, three shots clear of anyone else.
It was also a disappointing Friday for Tiger Woods, who dumped two balls in the lake at the punishing island green 17th and made a quadruple bogey seven en route to a 71 that left him nine strokes behind Fleetwood on three-under par.
McIlroy's electric round began at 1.59pm, but the four-time major victor was only signing his scorecard for a seven-under-par 65 after 7pm.
Rahm, who already has six worldwide victories in just short of three years as a pro, was still lagging behind when he made the turn, and then quickly moved to the top.
However, four birdies on the back nine salvaged his round to leave him very much in contention on Sunday. He drilled his second shot on the par-5 16th to the middle of the green and watched it feed to 12 feet away for his eagle.
By the end of the day, his 64 was about as high as it could have been. He'll go off with Fleetwood in the final pairing.
Given the nature of this golf course - and a forecast for a different wind - the fun might just be starting.
He has worked hard to control his temper and still let his passion carry him to great shots.
"It was a year of personal growth rather than golf game", Rahm said. "Yes [winning] is the end goal, but there's so many different little mini-goals you need to accomplish to get to that point".