Last season Leveni was the third defensive tackle for the Cowboys behind James Castleman and Ofa Hautau. He finished with 16 tackles, 11 unassisted tackles, 4.5 tackles for loss, a sack, and a quarterback hurry. Those may not sound like huge numbers but they are very solid for a third defensive tackle.
Leeini was due to be a strong force on the defensive line. This is an important injury that will call for younger defensive tackles to step up.
Leveni missed most of spring with a wrist injury, and my best guess is this is not the problem here and that Levini likely had an injury coming out of summer conditioning. We will see if OSU head coach Mike Gundy addresses the injury at the Big 12 Media Days.