CLEMSON, S.C. — Clemson center Jay Guillermo could disguise his unhappiness in front of his teammates, but the hoax had its limits. His face in the morning mirror, he said, made him shudder.

Guillermo had tried to cushion his fall from star offensive lineman in high school to banged-up backup in college with nightly drinking binges in the bars along College Avenue here in the fall of 2014. Pain lingered in his surgically repaired right foot, and he drank to heal that, too. By the end of December 2014, after weeks of drinking, Guillermo thought he was through as a football player. He was 20 years old.

“I would look in the mirror in the morning, and it was all negative thoughts,” he said. “I didn’t know a person could get so low.”

In January, Guillermo, regarded as one of the top high school linemen in the country in 2011, quit school and returned to his parents’ home in North Carolina. For six months, Guillermo said, he went through a personal atonement, which included substance-abuse counseling, an unorthodox fitness regimen and long talks with his grandfather, Ron Greene, a retired high school football coach.