The Seminoles (11-2, 2-1 ACC) scored the last five points in regulation to tie it at 77, then added five of the first six in overtime. Virginia didn't get a basket in the overtime until just 35.8 seconds remained, and they never did catch up.
Ralph Mims, a 94 percent free throw shooter for the Seminoles, hit a pair with 10.7 seconds left to give Florida State an 85-82 lead, and Thornton got a hand on J.R. Reynolds' 3-point try in the final seconds to preserve the Seminoles' victory.
The Cavaliers (7-6, 1-2), who started the game with only eight recruited scholarship players available, finished with five. Post players Jason Cain, Tunji Soroye and Laurynas Mikalauskas fouled out against the the bigger, physical Seminoles.
Isaiah Swann added 17 points for Florida State, which shot 60 percent overall.
Sean Singletary led Virginia with 27 points and Reynolds had 17.
In the overtime, Johnson scored down low to break the tie, and Thornton followed a free throw by Reynolds by making two of his own. Another by Johnson made it 82-78.
The game was close throughout, with Virginia taking its first lead since very early on two free throws by Singletary with 10:08 left. Neither team led by more than four thereafter. It was tied at 77 when the Seminoles inbounded with 39 seconds left.
Florida State thought it had grabbed the lead on Thornton's driving basket with 19.4 seconds left, but he was called for charging, giving Virginia a shot. On its two previous possessions, the Cavaliers had failed to get off a shot, each time all seeming to be watching and expecting Singletary to do something dramatic by himself.
This time, they worked the ball around before Mamadi Diane tried a buzzer-beating 3-pointer from the right corner, but the shot came up well short, bringing the OT.
The Seminoles used 11 players in the first half, trying to wear down the undermanned Cavaliers, and got scoring from eight of them. But Florida State went away from the breakneck pace after halftime, which seemed to help the Cavaliers.
Singletary had 16 of his points after the break and also finished with seven assists and seven rebounds. He made three 3-pointers and Reynolds made four.
Jason Rich added 12 points for the Seminoles.
FSU Tops UVA In OT
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