The Lawrence Journal-World reported the 18-year-old woman showed the officer text messages from Williams admitting to punching her in the arms during the Dec. 5 incident. The document says the officer also found the victim had bruises on her arms and side.
Williams reportedly told police that he pushed the woman when he saw her in a room with other men at an apartment building. Both have said they were in an intimate relationship.
His attorney entered a not guilty to a misdemeanor charge of domestic battery during a Dec. 7 court hearing.
Coach Les Miles says Pooka is suspended pending investigation.
Williams, a freshman running back from New Orleans, received several national and Big 12 honors during the 2018 season.