Elliott Fry got the Gamecocks on the board early in the first quarter with a 52-yard field goal with 9:47 to go in the opening frame.
Nunez opened play by helping the Gamecocks move the ball up the field.
Nunez, the first true freshman to start at South Carolina since Mikal Goodman in 1999, finished 12-of-22 passing for 184 yards.
South Carolina QB Lorenzo Nunez ran circles around the UCF defense.
As South Carolina's third starting quarterback in as many weeks, Nunez grew more confident as the game went on, leading the team to three touchdowns in the third period to overcome a 14-8 halftime deficit. But he began running when things broke down, eluding four tacklers - and getting a solid block from Nunez - he scored the touchdown that put the Gamecocks up for good.
And the 6-foot-3, 210-pound Nunez was out there front and center on Pharoh Cooper's game-changing 29-yard touchdown run, sealing off a UCF defender.
Head coach Steve Spurrier announced that Nunez would get the start against UCF on Tuesday. So while South Carolina should take this one easily, it could come down to which freshman quarterback makes the fewest mistakes, although Nunez' supporting cast should give him an edge.
ABOUT UCF (0-3): Stanback, who led the Knights with 697 rushing yards and10 touchdowns in 2014, had only 11 yards on 12 carries in UCF's first two games prior to sitting on the sidelines last week, ahead of his dismissal. But USC was unable to generate anything on the ensuing series when backup quarterback Perry Orth saw his only action of the half. Lorenzo Nunez threw two touchdown passes for the Gamecocks. 2.
"The first half was unacceptable to me, in my eyes", South Carolina linebacker Skai Moore said. The real difference was field position in the second half because of turnovers. "Those are the things that will cost you ball games".
"I think he played a little better than we all anticipated", Spurrier said. Not to beat a dead horse, but the DBs did a bad job on outside containment on Cooper's broken play TD; they also were the biggest "missed tackle" culprits on that play.
"I told one of the guys up top he's smarter than we are", Spurrier said with a laugh afterward. True freshman Tristan Payton caught five passes for 42 yards and returned two kickoffs for 48 yards.
But the spotlight, and pressure was mainly on Nunez, a highly touted dual-threat quarterback outside the norm of a classic Spurrier scheme. Central Florida recovered a fumbled punt by Pharoh Cooper on the 1-yard line and ran for a touchdown on the very next play.
Wide receiver Nick Patti would score on a keeper out of the Wild Knight package to give UCF a 7-5 lead.