Riegger watched as most of the field returned to the TPC at Heron Bay to complete the second round, and maintained the lead he built by reaching 12-under-par 132 on Friday.
Canadian Mike Weir played the final 14 holes of a 7-under-65 on Saturday to move within a shot of Riegger at 133, a stroke better than four players.
Riegger and Wier were to tee off in the final pairing of the day at 3:39 p.m. EST.
All four at 134 finished the second round early Saturday. Among them is former Arizona State standout Paul Casey of England, who finished off a 66.
Tied for third with Casey is the unheralded trio of Rod Pampling, Danny Ellis and Brett Wetterich.
Ninety-two players were forced to return to Heron Bay after two inches rain drenched the course on Thursday, preventing a third of the field from teeing off.
Riegger completed a course-record 9-under-par 63 early Friday, then shot a 3-under 69 to grab a two-stroke lead when play was suspended due to darkness.