"The speculation of me being too hung over and that's the reason I missed the meetings is absolutely incorrect," he said.
Manziel said he fell asleep without setting his alarm and his phone died during the night. He said he was rooming with Alabama quarterback AJ McCarron, but that McCarron didn't wake him up.
"I'm definitely not going to pin it on him," Manziel said. "It's my fault — 115, 120 percent."
He said he was disappointed he missed camp activities, but that there were "no hard feelings" between him and the Mannings. He said he's already been invited back to next summer's camp and looks forward to attending.
The early exit from the Manning camp is just part of Manziel's offseason in the public eye.
— He pleaded guilty on Monday to a misdemeanor of not identifying himself to a police officer following a 2012 altercation at a bar near campus in College Station.
— He sent out an update on Twitter in June saying that he "can't wait to leave" College Station, before quickly deleting the updated. He later apologized.
— He also created a minor stir in February when he said he took most of his classes online and didn't go on campus very much.
None of the transgressions were huge, but they combined to keep Johnny Football in the news and raise questions about his character.
Every move Manziel made on Wednesday was shadowed by a media throng. At one point, the quarterback said he felt like pop star Justin Bieber.
He talked about his friendship with NBA star LeBron James, his upcoming trip to the ESPYs and all the other positives that comes from his fame.
He said his carousing has been at times "blown out of proportion," though he did acknowledge that he needs to make better decisions because he's such a public figure.