Tag Riding, Mathew Goggin, Jeff Overton and Justin Leonard are tied for third at 12-under 204.
Heath Slocum is at 11-under 205 and a total of 19 players are within three shots of the lead.
"I'm going to have to play a lot better tomorrow than I did today. At least score better," Verplank said.
This event is the final one on the PGA Tour schedule and the last chance for players to move up on the all-important money list.
The top 125 are guaranteed fully exempt status on next year's tour, the top 30 on the year-end money list get invited to The Masters.