Contestants in the first of four PGA Tour playoff tournaments competed from dawn to dark to try to make up for the more than 5 hours of time lost because of weather delays on Thursday.
Slightly more than half the field completed the second round, but Kuchar was one of 41 stranded on the course when the action was halted.
Kuchar, who began the week in second place on the points list that will ultimately determine the winner of the FedEx Cup and the $10 million that goes with it, stood at 5-under par for the round through 13 holes at the Liberty National Golf Club.
He was 10-under for the tournament and one shot in front of both 2012 U.S. Open champion Webb Simpson and Gary Woodland.
Woodland finished his round as the sun was setting while Simpson resumed his first round early in the morning and played 30 holes. Both were at 133 for 36 holes.
"I had a 4:30 a.m. wake-up call," Simpson said. "It was a long day. All we did was walk and play golf."
Rose still had four holes to play while Fowler, Bradley and Scott were all in the clubhouse with a 135 total. Bradley broke the course record with an 8-under 63 in the second round.
Tiger Woods, ranked No. 1 in the world and No. 1 on the FedEx Cup points list, was 5-under with five holes remaining. Woods complained of a sore back prior to the tournament and he showed signs of discomfort Friday while playing the first 13 holes in 1-under.
British Open champion Phil Mickelson safely survived the 36-hole cut with a 140 total.
Kuchar was tied for the lead as daylight began to fade, but grabbed the top spot by himself when he hit his second shot at the par-5 13th to within 11 feet of the cup. Kuchar's putt for eagle narrowly missed, but the resulting birdie put him out front at the end of the day.
The top 100 on the points list from the 125 who began the week will advance to next week's Deutsche Bank Championship. Among those certain to be eliminated from the playoffs this week were Ben Crane, Charlie Wi, Johnson Wagner and former U.S. Open champion Lucas Glover.