Fitzpatrick made light of the cold, breezy conditions to card a superb 67 and end a rollercoaster day three shots behind pacesetter Mito Pereira, the PGA Tour rookie continuing to impress on just his second major start.
Pereira went from one behind playing partner Will Zalatoris to four ahead in the space of six holes, then saw his lead cut to a single shot after four bogeys in five holes around the turn before back-to-back birdies on 13 and 14.
The 27-year-old from Chile also birdied the last to card a 69 and finish nine under par, with Fitzpatrick and Zalatoris – who recovered from playing his first seven holes in four over to return a 73 – on six under.
“I was so proud of myself after my start today,” said Fitzpatrick, who fought back superbly after dropping shots on the first two holes.
“To get back to the same score I started on at the end of the front nine I was absolutely delighted and I’ve put myself in a good position.”
“I feel good, my game is in a good spot,” said Power, who was ranked outside the world’s top 400 just a year ago but is currently ranked 42nd.
“Obviously I’ll go out a little before any of the leaders. If I can get a couple birdies on the card, it can make the world of difference and then you need a couple breaks to go your way.”
McIlroy began the day five shots off the lead but dropped four shots in three holes from the sixth before a birdie on the ninth seemingly steadied the ship.
A triple bogey on the 11th effectively ended the first round leader’s chances and although he birdied the 13th and came agonisingly close to a hole-in-one on the next, a birdie on the 16th was followed by a three-putt bogey on the last.
Having made the cut on the mark of four over par, American Webb Simpson jumped 54 places up the leaderboard courtesy of a superb 65, the lowest score of the day.
“I think it’s probably top two or three best rounds I’ve ever had in a major, considering the conditions,” Simpson said.
“Today was a test of the mind as well as physically because we have a mist out there all day, clubface is getting a little wet, it’s blowing sideways.
“We’ve gone from 92 degrees to what we had today, so the ball is going way shorter. So there’s a lot of adjusting on the fly, and I typically don’t like to play when it’s colder weather, so I surprised myself a bit today. But I’ll take it.”
Simpson’s score was what Tiger Woods had been targeting after making the halfway cut with a shot to spare, but the 15-time major winner struggled to a 79 and admitted afterwards he was not certain to play the final round.
“Well, I’m sore. I know that for a fact,” Woods said. “We’ll do some work and see how it goes.”