Clark injured his knee during the second half of Michigan's 49-10 victory over Penn State on Saturday. The redshirt senior started each of the Wolverines' first four games, recording 10 tackles with three pass breakups.
Harbaugh said the team would explore the option of petitioning the NCAA to get Clark a sixth year of eligibility.
Clark was carted off the field on Saturday. Many of his teammates came off the sideline to send him off.
"I don't [know] if I've ever seen that before, and it was the same way in the locker room afterward," Harbaugh said. "He's a highly respected member of this team."
Michigan's secondary got a boost during the Penn State game, when All-America cornerback Jourdan Lewis returned to the lineup for the first time this season. He missed the first three games of the year with muscle strains in his back and upper leg.