Yet, it's a little early to say the Sooners' defense will never recover from the loss.
Sophomore linebacker Jordan Evans could be poised to replace Shannon in the starting lineup and has shown signs he could lessen the impact of Shannon's absence on the Sooners' College Football Playoff hopes.
In fact, he's already done it before.
When Shannon missed the bulk of the Sooners' 38-30 win against Texas Tech a year ago, Evans filled in with eight tackles as a true freshman against the Red Raiders. Despite playing a minimal role during his first six games as a Sooner, Evans was all over the field against Tech, making plays in the running and passing game to help OU overcome the loss of Shannon. By comparison, Shannon averaged seven tackles per game last season.
"I have confidence in Jordan," linebacker Eric Striker said this spring. "When he came in for Texas Tech, he had a lot of pop to him, so I always had confidence in him."
While there's no replacing an experienced, productive linebacker like Shannon without some hiccups, Evans would bring terrific athleticism and good size to the Sooners' defense at 6-foot-3, 223 pounds. In fact, Evans was one of the stars of OU's spring game, with his hit on receiver K.J. Young serving as one of the highlights of the day.
"Jordan has really improved and is much more sound and disciplined in schemes and where he needs to be," Stoops said after the spring game. "He has got great range and great athleticism."
Behind Evans, assuming he does secure a starting role, is where the impact of Shannon's possible suspension could hurt the most. Senior linebacker Aaron Franklin could be an option and provide depth behind Evans and 2013 Big 12 Defensive Newcomer of the Year Dominique Alexander, the starter at the other inside linebacker spot. But, quite frankly, the Sooners will need someone to step up behind their sophomore linebacking duo if they hope to overcome any additional setbacks at the position this fall.