Des Plaines police Chief Jim Prandini said Daniel Rago slapped Hester in the back of his head while the Bears star was in a cashier's line at the Rivers Casino in Des Plaines about 10:40 p.m. Friday, the Chicago Sun-Times reported.
Rago then walked away, and Hester did not retaliate, Prandini said.
There had been "no incident" between Rago and Hester before the slap and "no physical confrontation between them" after, Prandini said.
Rago gave no reason for slapping Hester, Prandini said. The police chief said Rago "had been drinking."
Rago was released on bail and is to appear at a court hearing in Skokie in December.
Neighbors in Rago's Mount Prospect community described him as a friendly ardent Chicago sports fan and expressed surprise he had been accused of slapping the Bears player.
"He's a very nice guy. ... As far as being aggressive -- not at all," said neighbor Kathy Connolly.
She said Rago is a Cubs season ticket-holder who often offers her tickets when he can't use them.