Half a minute after tying the game, Ben Diamond hit a jumper in the lane with 45 seconds left to play to put the Rebels out front for good at 70-68.
Diamond led all scorers with 28 points, getting 16 in the second half.
South (21-3, 9-0) secured at least a top-two seed for the District 1-AA tournament. Sullivan East (12-12, 5-3) dropped a game behind Elizabethton in third place.
Neither team ever led by more than six points, and both finished with 10 total 3-pointers.
Sullivan East took a 67-66 edge on a Dylan Bartley 3-pointer with 2:11 showing on the clock. Bartley totaled three treys and finished with 23 points. Eric Hare chipped in a dozen and Austin Davis totaled 10.
Cole Layne contributed 19 points for South, which swept the season series with the Patriots by a combined 11 points.
BALANCE BOOSTS LADY PATRIOTS
The Lady Patriots also swept the season series with their cross-county rivals thanks to a no-doubt 58-23 victory.
Sullivan East (16-9, 6-2) had all the answers for the Lady Rebels. Balanced scoring helped the Lady Patriots to a 31-17 halftime lead and that margin kept growing in the second half. Hayley Grubb finished with a team-best 16 points, Jenna Hare tossed in 11 and Emma Aubrey hit a set of three 3-pointers for nine.
The Lady Rebels (8-15, 2-6) had a trio of players — Nicole Troutman, Chloe Nelson and McKenzie Littleton — score four points apiece.
TREY OF MILESTONES
Diamond, Layne and the Lady Rebels’ Alex Harris all have each reached the 1,000-point plateau this season.
Sullivan South takes a trip to Volunteer on Friday for a nonconference matchup.
Sullivan East travels to Unicoi County for a Friday meeting.