Kyle Thompson (68), John Merrick (69) and Craig Bowden (71) are knotted in second place at 7-under-par 209 at the Upper Course at Peek'n Peak Resort.
Overnight leader Jason Dufner struggled on Saturday. He shot a 1-over 73 and is tied for fifth place with Tom Scherrer (68), Gavin Coles (70) and Charlie Wi (72). The group finished 54 holes at minus-6.
Pratt flew out of the gate on Saturday. He collected three birdies in his first four holes, but cooled a bit. Pratt parred his final five holes on the front side to make the turn at 3-under 33.
Things came apart quickly on the back nine. Pratt bogeyed the 10th, then two holes later, came up short and left with his tee ball at the par-3 12th. Pratt chipped to 12 feet, but missed the par chance to fall back into a tie for the lead at minus-7.
Pratt knocked his approach from a fairway bunker to 15 feet at the closing hole and snaked in the birdie try. He will take the 54-hole lead for the first for the first time in his brief Nationwide Tour career.
Pratt played a few Nationwide Tour events last year, including a runner-up finish at the Xerox Classic. This year, Pratt has teed it up in six events, including the Peek'n Peak Classic, and his best finish was a tie for fourth place at the Henrico County Open in May.
'A couple under out there is not a bad score today because it's playing so hard,' said Pratt, who is winless in his two years on the Nationwide Tour. 'I have been playing pretty good this year. Hopefully I can keep it going.'
Thompson was flawless on Saturday with four birdies, all on the front nine, and zero bogeys.
Merrick recorded three birdies on his front side, then had an up-and-down back nine. He mixed three birdies, three bogeys and three pars, but had a chance to match Pratt in the lead at 18. Merrick missed a 7-footer for birdie on the closing hole, but is within one of the lead in his quest for victory No. 1 on the Nationwide Tour.
Bowden moved up the leaderboard with a 20-foot birdie putt at the ninth and a 3-footer for birdie at 10. He bogeyed the par-5 14th, but is in the hunt.
'It was a tough day,' admitted Bowden. 'I hit a lot of good shots with the way the wind blew. I gave myself some opportunities, but I couldn't get one to go in.'
Chris Anderson (68) and Peter Tomasulo (69) are knotted in ninth place at 5-under-par 211.