Hill, who saw action in four games as a true freshman last season, beat out heralded recruit Kyle Allen during summer practice to get the first crack at replacing 2012 Heisman Trophy winner and current Cleveland Browns rookie Johnny Manziel under center.
Allen was rated as the nation's top quarterback prospect of the 2014 recruiting class by rivals.com.
"The competition was close and that competition will continue to help us improve," Sumlin said. "I have talked to both quarterbacks as well as the team and we will prepare with Kenny getting the first-team reps."
Hill completed 16-of-22 passes for 183 yards and one touchdown last season, adding 37 rushing yards on seven attempts.
Texas A&M is ranked 20th in the Amway/USA Today preseason coaches poll, while South Carolina came in at No. 9 in the initial rankings.