Christophe Varidel came off the bench for 13 points, Eric McKnight added 12 and Bernard Thompson 11 for the Eagles (11-6, 3-1), who led 40-29 at halftime but watched North Florida build a 66-60 lead with 6 minutes left to play.
McKnight and Fieler hit back-to-back layups to spark an 11-2 run that put Florida Gulf Coast up 71-68 with 2:31 left.
A Parker Smith 3-pointer tied the game at 71 with 1:45 left to play but Fielder made a layup to put his team ahead 73-71. North Florida (7-10, 2-2) then missed three straight shots -- a layup and two 3-pointers -on the same possession before Brown grabbed the rebound.
The senior guard sank 1 of 2 attempts to seal it.
Mike Krzyzewski says he has good reason to be excited for next season thanks to a combination of Duke's incoming freshmen and a core of experienced upperclassmen.
Georgia guard Juwan Parker has been awarded a medical redshirt, leaving him with two years of eligibility, after missing the 2015-16 season with a partially torn Achilles tendon.
Forward Trevon Bluiett has withdrawn from consideration from the NBA draft and will return to Xavier for his junior season.