USA Today reported Manziel was spotted dining and gambling at Las Vegas' Planet Hollywood casino.
Waitress Tina Samira told the newspaper she served Manziel and his guests at Heart Bar at Planet Hollywood. Manziel also sat down at a blackjack table and a casino employee examining his photo ID exclaimed, "We've got Johnny Manziel with us tonight," patron John Hornacek told USA Today.
Manziel is not at FirstEnergy Stadium for Sunday's season finale against the Pittsburgh Steelers, and he's not required to attend because he's in the NFL's concussion protocol, a team spokesman said.
The spokesman didn't comment when asked whether Manziel, who was diagnosed with a concussion by team doctors Wednesday, spent Saturday night in Las Vegas.