There were several reports earlier Sunday that said Manziel was sent home by Archie Manning because of "partying" but camp officials said those reports were not true.
"Johnny Manziel did participate in some activities in the 2013 Manning Passing Academy as a college counselor/coach," the statement said. "After missing and being late for practice assignments, Johnny explained that he had been feeling ill. Consequently, we agreed that it was in everyone's best interest for him to go home a day early."
Manziel, last season's Heisman Trophy winner, was at the academy, held at Nicholls State University in Thibodaux, La., as a college coach and counselor. He threw for 3,706 yards with 26 touchdowns and nine interceptions last season.
"I enjoyed meeting Johnny," said Broncos quarterback Peyton Manning. "I can remember a 20-year-old Eli [Manning] missing a meeting and catching some flak. We always have counselors who leave early. Johnny was great with the campers for the time he was here. He had to leave early. I wish him the best and I want him to come back as a counselor next year."