Vikings big question: How significant will Jordan Hicks' absence be?

The shin injury linebacker Jordan Hicks sustained on Sunday became serious enough that the Vikings medical staff recommended he be evaluated at a local hospital, out of concern that the swelling in his lower leg could cause compartment syndrome and restrict blood flow to his muscles. The linebacker had surgery to relieve the pressure in his leg and was still in the hospital on Monday. Coach Kevin O'Connell said the surgery was successful and Hicks is doing well, but he added that the 31-year-old wouldn't play Sunday in Denver.

With Hicks out, the Vikings brought Anthony Barr, 31, back to their practice squad, signing the four-time Pro Bowl player who spent eight years playing some of the roles in Mike Zimmer's defense that Hicks plays in Brian Flores' scheme. Barr, the first player the Vikings drafted under Zimmer in 2014, was responsible for running the Vikings' defensive huddle and setting their defensive front while playing a vital role in the double-A gap blitzes Zimmer frequently called.

He might not play such a central role for the Vikings immediately, but the fact the team signed him Monday afternoon does seem like a reflection of how significant Hicks' absence could be. The veteran has been integral to a Vikings defense that now ranks 13th in yards allowed per game and ninth in expected points added per play. Though the group's blitz rate has dipped to 45.3%, it's still the highest in the league; the defense has managed to be aggressive without getting burned downfield because of the system of checks that players such as Hicks and Harrison Smith make before the snap.

The Vikings will turn command of the huddle over to undrafted rookie Ivan Pace Jr. in Hicks' absence, and they'll lean on heady veterans such as Smith and Josh Metellus with Hicks out. The role, though, could still mean an uptick in Pace's playing time. He was on the field for 82% of the Vikings' defensive snaps against the Falcons last week and 76% of defensive snaps against the Saints on Sunday; his snap percentages the past four weeks have been his four highest of the season. With the Vikings' defensive headset in his helmet, Pace might not leave the field at all.

"We've got possibilities based upon the packages we put on the field, but it is a unique thing because that [headset], you don't want to be in a situation where you're taking one helmet off and handing it to another [player] snap in and snap out," O'Connell said. "Ivan handled it in the preseason. That was one of the things that really jumped out at us, how well he handled leading those groups, and he's had some work at it throughout the season, kind of in spot duty. We've got to get him ready to go, and I know Flo and his group will do a good job with that."

Pace should have a quieter environment on the road in Denver, and he's shown himself ready to handle just about everything the Vikings have asked to this point. Hicks' absence, however long it lasts, will test the Vikings defense. The group has adapted to the loss of Marcus Davenport because of a high ankle sprain and curtailed the run defense issues it had early this season. With Hicks out, the defense will face another challenge; the decision to bring in Barr could be an attempt to recoup some of the situational acumen the Vikings will miss with Hicks sidelined.