Buckley opened the contest with 11 of USF's first 15 points, including three treys. Freshman guard Amu Saaka scored six of the Bulls' next eight points as USF took the 23-15 lead with 9:24 remaining in the first half.
A 14-6 run by Stetson over the next nine minutes knotted the game at 29 going into the locker rooms for halftime.
After the five-minute mark, Mattis forced a turnover, which led to a three by Buckley, his fifth of the night, narrowing the Stetson lead to just one field goal.
Buckley's layup at 1:40 tied the game, but the Hatters quickly answered with a two-point bucket of their own. With 16 seconds remaining, freshman guard Solomon Bozeman toed up to the line, hitting both free shots to tie the game at 59.
A missed 15-foot jumper by Stetson with one second remaining in regulation sent the game into overtime.
Down by four halfway through the extra period, Buckley stole a Stetson inbounds pass then assisted a Mattis layup to bring the score within two, 64-66. Mattis then tied the game at 66 apiece with 30 seconds remaining, forcing the contest into double-overtime.
With 51 seconds left in the second extra period, freshman guard Amu Saaka converted a layup to put the Bulls up by four, but the Hatters answered with two free throws. In the end, Bozeman hit 3-of-4 from the charity stripe to secure the 77-72 USF victory.
USF hit 17-of-21 free throws in the final 15 minutes of the game to get the win over the in-state foe.
Mattis ended the game with 20 points, seven blocks and five rebounds while Bozeman added 17 points (15-16 from the line) and seven rebounds in USF's fourth win of the year.
USF concludes its five-straight games at home to begin the year on Dec. 5, as the Bulls tip off with the Richmond Spiders at 7 p.m. in the Sun Dome.
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