Monday was a rough day for the Green Bay Packers defense. Linebacker Jake Ryan and safety Kentrell Brice both had to be carted off after suffering leg injuries during practice. It could turn out to be even worse if the fears about Ryan’s injury turn out to be true.

According to Ian Rapoport of NFL Network, Packers head coach Mike McCarthy says Ryan is still undergoing tests to confirm the severity of his injury. Although, a source within the Packers says the fear is that Ryan may have suffered a serious knee injury.

“He was just devastated,” linebacker Blake Martinez said, per Rob Demovsky of ESPN.com. “Obviously, he was super-excited about the season. He’s been putting a tremendous amount of work in. He’s been awesome throughout OTAs and these past four practices. It’s been good for him. It’s just really tough.”

Ryan, 26, was a fourth-round pick by the Packers in 2015. He's emerged as a reliable starter at linebacker for the Packers, starting 22 out of his last 29 games for Green Bay over the last two years. He had 79 tackles and a sack in 15 games (12 starts) last season.

It would be a huge blow for Ryan if his knee injury is indeed serious. He’s in the final year of his contract and needs a strong year this season in order to land a big deal in free agency.

If Ryan is to miss a significant amount of time this season, rookie linebackers Oren Burks (a third-rounder) and Greer Martini (undrafted) could see more action in their first season in Green Bay.