Vaughn Taylor, who was one shot behind Utley to start the third round, carded a 2-under 70 to finish five shots off the pace at 11-under-par 205. He was joined by Bo Van Pelt, Guy Boros and Bob Heintz in a tie for third.
Utley got off to a quick start with two birdies over his first four holes. He then added a birdie at the par-4 seventh but found trouble with a bogey at the eighth to make the turn at 12-under.
'Honestly, I didn't hit it quite as good today,' said Utley.
The 41-year-old tallied a birdie at the 11th but stumbled again with a bogey at the par-three 13th. Utley, a three-time winner on the Nationwide Tour, countered brilliantly with three consecutive birdies starting at the par-5 14th.
Utley notched his last birdie of the day at the par-4 18th and stands in good position to earn his first title since 1995.
'I was playing pretty good and snuck out a couple of birdies but coming in it got kind of silly,' said Utley, who ran home several long putts down the stretch. 'I made a bunch of long ones and those are the things that you just have to ride out when it starts happening.
'You try not to think about it. I work off swing thoughts and I had a thought working with my stroke. I just tried to stick with it.'
Bertsch picked up three birdies on the outward nine to quickly move to 11-under par. He caught fire down the stretch with a birdie at the 14th and back- to-back birdies starting at the 16th but capped his round with a bogey at the last, the only blemish in his round.
Zach Johnson, who won this year's Rheem Classic in a playoff, posted a 4- under 68 to finish in a tie for seventh alongside Paul Claxton and Scott Sterling at 10-under-par 206.
Tommy Tolles, Bubba Watson and Todd Demsey were one shot further back at 9-under-par 207.
Tom Scherrer, Jeff Gove, Kevin Shields, Roland Thatcher and Franklin Langham are tied at 8-under-par 208.