Kris Cox fired the lowest round of the week on Saturday with a 7-under 63 and is alone in third place at minus-6.
Herron flew out of the gate on Saturday with birdies at three, five and six. He drained a 14-foot birdie putt at the par-4 ninth to move to 9 under par and take a three-shot lead.
After his run on the front nine, Herron began missing makeable putts. His 6-foot birdie effort on the 11th stayed above ground and the balky putter would become a theme for the remainder of his round.
Trouble loomed large for the Colonial winner. At the 12th, he drove into the left rough, then knocked his approach in the water. Herron took a drop and hit his fourth to 8 feet, where he rolled in his bogey putt.
Two holes later, Herron missed the green at the par-3. He chipped to 9 feet and that putt did not fall. Suddenly Herron's once large front-nine lead disappeared to a single stroke.
The shrinking gap in the scores also had something to do with Pernice's play. He overcame two bogeys on the front side, then ran home a 20-foot birdie putt at the ninth. Pernice birdied the par-3 11th to get to 5 under par.
With Herron now at 7 under par, Pernice clawed within one at the 14th. Pernice sank a 25-foot birdie putt there and tied Herron for the lead with a 15-footer for birdie at the very next hole.
Both players struggled on the way into the clubhouse. Herron drove way right into the trees, then landed in a greenside bunker with his second. He blasted out to 7 feet, but that putt, like many others for Herron on Saturday, did not go.
Pernice played the 16th badly as well as his chance for birdie came from the fringe. He made a par, as Herron finally got his flat stick working at 17 where he converted a par from 5 feet.
Pernice had even longer for par at the 17th as his drive found the left rough. He pitched out then hit his third to 7 feet. Pernice made that par putt, then both players made pars on 18 from off the green.
The two friends will battle it out in Sunday's final group. Herron can collect wins in back-to-back weeks and join Phil Mickelson, who did it at the BellSouth Classic and Masters, as the only players to accomplish the feat this year on the PGA TOUR.
If Pernice visits the winner's circle on Sunday, it will be for the third time on the PGA TOUR. He has not hoisted a trophy on TOUR since 2001 at The International.
'I have to go out tomorrow and commit to shots,' said Herron. 'I kind of guided it the last few holes. I hung in there the last few holes to give me some momentum.'
'I hit the ball beautifully on the front nine, three-putted twice and never made a birdie,' said Pernice. 'All of a sudden, I snuck one in on No. 9 and that got me going a little bit.'
Jeff Maggert (68) and Ryan Palmer (69) are tied for sixth place at 4-under-par 206. Two-time winner Nick Price (69), Briny Baird (68) and tour rookie Camilo Villegas (71) are knotted in eighth place at minus-3.