Sheehan played just one hole, which he birdied, before play was halted due to darkness. It was delayed some 7 1/2 hours at the start of the day due to rain.
Play is scheduled to resume Sunday at 8:30 a.m. EDT, but the course was hit with another heavy shower Saturday night.
"Hopefully, we can start the fourth and final round about (12:15 to probably 2:05). If we can do that, we can finish tomorrow," tournament director Mark Russell said.
Worst-case scenario is completing the final round on Monday.
The leaders are tied at 5-under-par, one shot ahead of seven golfers, including 2002 champion Vijay Singh of Fiji.