Nitties, the 26-year-old Australian who appeared on the Golf Channels Big Break series, had a 12-under 132 total. He birdied the final two holes, his eighth and ninth birdies in the bogey-free round.
Garrigus and Frazar shot 64s on the TPC Stadium Course. The 108-hole event will end Monday with the top 25 and ties earning cards.
Bryan DeCorso (68), Geoffrey Sisk (65), James Oh (63), Diego Vanegas (64), Troy Kelly (68), Gary Woodland (64) and Tyler Aldridge (66) were 10 under, and former PGA winner Mark Brooks (69) was 9 under along with Jay Williamson (68), Major Manning (70) and Ted Purdy (67). Williamson reached the FedEx Cup third round, but failed to keep his card.
Former U.S. Amateur champion Ricky Barnes already earned his card by finishing 25th on the Nationwide Tour money list, but entered the final stage to improve his status. He was tied for 68th at 4 under after a 68 on the TPC Stadium Course.