Job No. 1 for Oklahoma coach Lincoln Riley and new defensive coordinator Alex Grinch is fixing a defense that got torched last year despite the Sooners making the College Football Playoff. That construction process has been delayed a bit due to a couple of injuries to two key defenders.

Senior linebacker Caleb Kelly and redshirt freshman defensive lineman Jordan Kelley each sustained lower body injuries and will be out for the foreseeable future, Riley announced on Thursday. It was later specified by 247Sports that both players suffered ACL injuries. 

"It's a really tough deal for both Caleb and Jordan," Riley said in a statement. "I guess if there's a silver lining it's the timing of the injuries with them occurring five months before the season. I know they'll work their tails off to get back to the field as quickly as possible, and we'll be there with them every step of the way."

Kelly's injury will require surgery, and Kelley has already undergone surgery for his injury. It's a big blow to a defense that is in desperate need of a spark. 

Kelly, a former five-star prospect in the class of 2016 and the No. 24 overall player in the country, had 61 tackles, 4.5 tackles for loss and three sacks as a junior in 2018. He added one fumble recovery for a touchdown in a big win in the regular season finale at West Virginia. He had recently moved to the "Will" linebacker spot after spending some time inside for the Sooners last year, and is expected to be the centerpiece of the new-look defense. Sophomore linebackers Dashaun White and Levi Draper could step in for the time being, while Kelly recovers from his impending surgery.

Kelley only played in two games last season and took a redshirt. He did notch two tackles in the home win over UCLA in Week 2. The 6-foot-3, 297-pounder was a three-star prospect in the class of 2018, and is expected to be a contributor along the defensive line once he returns to form.

Oklahoma will play its spring game on Saturday, April 13 at 4 p.m. ET.