MADISON, WISC. -- Authorities say a group of men attacked star Wisconsin running back Montee Ball early Wednesday morning, knocking him to the ground and causing injuries that sent him to the hospital.

Police say five men jumed Ball around 2:15 a.m. near campus. They knocked him down and kicked him.

Ball, a finalist for the Heisman Trophy last season, was taken to a hospital with head injuries. Coach Bret Bielema said Ball has been released and is under the care of the school's sports medicine staff. Bielema says he expects Ball will make a full recovery, but did not address Ball's availability. The season opens Sept. 1 against Northern Iowa.

Ball tweeted the following: "I appreciate the support and thank you for the concerns. I will be okay! See you guys in September! #WiscONsin"

Police say Ball apparently didn;t know who the men were.