Tony Kemp led off with a single and the top-seeded Commodores (49-8) eventually loaded the bases with one out against three relievers.
The Gamecocks (39-18) had intentionally walked Connor Harrell, who had two hits. Gregor delivered his second single of the game to score Kemp.
Carson Fulmer (2-0) gave up three hits and one run in the final 41/3 innings for Vanderbilt.
Harrell, Gregor and Vince Conde had two hits each for the Commodores.
South Carolina’s LB Dantzler had tied the game at 3-3 with a homer in the seventh after Vanderbilt opened a 3-0 lead.
Max Schrock, Joey Pankake and Brison Celek had two hits apiece for the Gamecocks.
South Carolina starter Jordan Montgomery allowed three unearned runs and stuck out eight in 7⅔ innings. Adam Westmoreland (7-3) took the loss. He allowed one run on one hit in ⅔ of an inning.
Vanderbilt starter Kevin Ziomek went 5⅔ innings and allowed two runs on eight hits with a walk and four strikeouts.
South Carolina dropped into the loser’s bracket after a 5-3 loss to Mississippi State on Wednesday night.