The 46-year-old Kuchar is the only player to reach all 17 postseasons in FedEx Cup history since its inception in 2007.
The top 70 will qualify for the playoff opener next week in Tennessee, with American veteran Kuchar currently well back in 113th spot in the FedEx rankings.
Nine-time tour winner Kuchar hasn't lifted a title in five years, though he tied for third place two weeks ago in the 3M Open.
"It's certainly been a frustrating year, but I feel like the bar's been set high," Kuchar said.
"I feel like I played a lot of good golf, consistent golf for a long time. Makes the, I guess, poor golf that much more frustrating."
Kuchar is facing a 36-hole on Sunday at Sedgefield Country Club at Greensboro, North Carolina with the event washed out by rain on Thursday and delayed Friday and Saturday. Twenty players were unable to finish play Saturday.
Americans Chad Ramey (64), Max Greyserman (60) and Cameron Young (62) were tied second, a shot behind Kuchar, with Billy Horschel (68), Beau Hossler (70) and England's Aaron Rai (65) a further stroke back.
The two Australians left in the field were well out of contention - Min Woo Lee (71, tied 107th at even par) and Cam Davis (73, tied 121st at two over). Aaron Baddeley withdrew after his opening 71.
Kuchar was looking to draw on some recent experience.
"I've got some built-in confidence knowing that a month or two ago when I was down at the US Open qualifying, did 36 holes at the Bear's Club, was medallist down there," Kuchar said. "Able to walk 36 in the heat and humidity without too much problem."
With players allowed to lift, clean and place their golf balls in the fairways because of the wet conditions, Kuchar moved up the leaderboard with late birdies on Nos. 5-7.
Hossler parred the final three holes in his 60. There have been 14 sub-60 rounds in PGA Tour history, with Brandt Snedeker shooting 59 at Sedgefield in his 2018 victory.
Jordan Spieth, at No. 62 in FedEx Cup standings, missed the cut with rounds of 67 and 71. He was playing the event for the first time since 2020.
