Leading by three shots at 8-under-par, Morgan played his final five holes in 3-over-par to finish the day at 5-under. Meanwhile, Nelson played the same stretch of holes in 3-under to take the top spot entering the weekend.
Nelson is vying for his third win in as many starts, while Morgan is seeking his second straight title defense.
Four-under-par on the day through his first six holes, Morgan finished with a 1-under-par 69. Nelson was only 2-under for the tournament through nine holes on Saturday, but birdied the 10th, 14th, 16th, 17th and 18th to move one shot lower than Morgan at 6-under-par. Nelson's lone blemish in a back nine 31 was a bogey at the par-4 15th.
Hubert Green is two shots back of Nelson after an even par round of 70 at the Grizzly course in Mason, Ohio. Allen Doyle, Bruce Fleisher, John Mahaffey and Bruce Summerhays are all tied for 4th at 3-under-par.