Posted by ESPN.com's Adam Rittenberg
Northwestern senior linebacker Malcolm Arrington will have a MRI on his left knee after sustaining an injury in the first half of today's win against Purdue. A team spokesman said Northwestern hopes to have an update on Arrington by Monday.
The injury didn't look good on TV replays, and Arrington likely will miss some time. He ranks third on the team in tackles (51) and fourth in tackles for loss (6.5). Sophomore Nate Williams replaced Arrington against Purdue and likely will start next week at Indiana if Arrington can't play.