The injury also will keep Northwestern's star running back/returner sidelined for the spring.
Mark is one of 11 Wildcats players out for spring ball following winter surgeries. Northwestern opens practice on Wednesday.
Other notables sitting out include defensive tackle Sean McEvilly (foot) and defensive ends Ifeadi Odenigbo (shoulder) and Deonte Gibson (shoulder), all potential starters this fall. Cornerback Daniel Jones and running back Stephen Buckley both are recovering from knee injuries sustained during the 2013 season.
Last spring, Northwestern lacked bodies along the offensive line because of winter surgeries. It altered practices and arguably cost the Wildcats during the season. This year, the defensive line will be thin as McEvilly, Odenigbo, Gibson and tackle Max Chapman all are out for the spring session.
"Our numbers will be down there," Northwestern coach Pat Fitzgerald told ESPN.com. "Would you notice watching practice? Maybe not. We'll probably take more breaks during scrimmage days. It's kind of the reverse of last year, so we'll have to do a better job than a year ago.
"The depth is good; I don't think the depth is great in spring. That's going to be an area we're really going to have to improve in camp."