Nelson and Thorpe are one shot clear of Bob Murphy, Hale Irwin, Dana Quigley and John Mahaffey.
Rain cancelled Fridays first round at Kings Islands in Mason, OH, forcing a restart on Saturday. The event has been reduced to 36 holes, with the final 18 being played Sunday on the Grizzly Course.
'Knowing it's a two-day tournament, you could shoot yourself out of it,' Nelson said. 'You couldn't win it today, but you could definitely put yourself in a position where you couldn't win tomorrow.'
Nelson, a four-time winner in 2001, recorded one eagle, five birdies and two bogeys on Saturday, as did Thorpe. Both men eagled the par-5 4th.
Full-field scores from the Kroger Senior Classic