Wisconsin senior running back Montee Ball was the victim of what police are calling an "unprovoked assault" early Wednesday in Madison, Wis.

Montee Ball was the Big Ten's Offensive Player of the Year in 2011 after scoring 39 touchdowns and gaining 2,229 total yards. Jonathan Daniel/Getty Images

Ball was attacked by five men near Wisconsin's campus around 2:15 a.m. Wednesday. Witnesses told police the men knocked Ball to the ground and began kicking him. Ball, a 2011 Heisman Trophy finalist, was taken to a hospital. A team spokesman said Ball spent two hours in the hospital before he was released. It is not known if he can practice Monday when camp opens. Wisconsin opens the season Sept. 1 at home against Northern Iowa.

Bull suffered a concussion and facial injuries, the school said. There is no timetable on his return.

"My concern right now is for Montee's health and well-being," Wisconsin coach Bret Bielema said in a prepared statement. "Montee has been released from the hospital and is under the care and supervision of our sports medicine staff. We will continue to evaluate him as we approach the start of fall camp this weekend. I do expect Montee to make a full recovery."

According to an incident report, Ball didn't appear to know his attackers.

Ball was walking with two friends on the 500 block of University Avenue. The two friends were walking ahead of Ball, and turned around to see five men jump him, knock him to the ground and begin kicking him in the head and torso. Several people came to Ball's aid, including a man walking on the other side of the street, and ran off the attackers.

"We believe this is an unprovoked attack. We're trying to determine if this victim was targeted for who he is," said Joel DeSpain, the public information officer from the Madison police department. He added that this area of Madison has had a lot of crime lately, and police have devoted additional officers to patrol it.

There was no indication from the original interviews that the attack was a robbery. Ball's cell phone is unaccounted for, but police aren't sure whether or not it was taken by one of the attackers. If so, the incident will be investigated as a "substantial battery and robbery."

Detectives are expected to interview Ball again Wednesday, as well as talk to witnesses at the scene.

Police are looking at surveillance video both inside and outside some of the bars and establishments on University Ave.

In a post to his Twitter account Wednesday, Ball tried to assure his fans that he was OK.

"I appreciate the support and thank you for the concerns.I will be okay! See you guys in September! #WiscONsin," he wrote.