Alex Noren, of Sweden, Spain's Jon Rahm, J.B. Holmes and Chez Reavie shot 68s and are one stroke back at the TPC Sawgrass Stadium Course in Ponte Vedra Beach, Florida.
"Very pleased. One of those days where I kept out of trouble," said Hughes, of Hamilton, Ontario. "When I missed the greens I did it in the right spots and when I needed a par I was able to do it."
South Africa's Louis Oosthuizen and Francesco Molinari of Italy head a list of 11 players who shot 69 and are two strokes off the lead.
World number one Dustin Johnson tops a large group at 71 that also includes German Bernhard Langer, who at 59 is the oldest player in the tournament.
Jordan Spieth, Rory McIlroy, Justin Thomas, and this year's Masters champion Sergio Garcia all shot 73.
Garcia's round was highlighted by a hole in one on the island hole No. 17. Garcia is the second to achieve the feat in as many years following Willy Wilcox's previous ace on the par-three.
"The feeling was great," Garcia said. "I think I wasn't quite in the tournament because of everything that's been going on after the Masters win and media and people congratulating you left, right and centre.
"I felt like I was a little bit up in the clouds, and when I woke up, I was 4 over after six."
McGirt had three birdies on the front nine and eagled both of the par-fives on the back nine to offset two bogeys. Last year's Memorial Tournament winner McGirt is just the 26th player to record two eagles in one round during The Players Championship.
Hughes had a solid round of five birdies and no bogeys. He is also a one-time winner, capturing the 2017 RSM Classic in October.
Last year's Masters champion Danny Willett shot a 79.
David Toms (back) and Kevin Na (illness) withdrew from the tournament during Thursday's round.
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