If Ndulue is unavailable for the Sooners' 2013 season opener — scheduled for Aug. 31 at home against Louisiana-Monroe — that would leave OU with just four returning defensive tackles.
Sophomore Jordan Phillips is the most experienced defensive tackle, having played in 11 games last season. Junior Torrea Peterson has played sparingly throughout his career, and redshirt freshman Jordan Wade has yet to appear in a collegiate game.
Junior Rashod Favors, a former defensive end, converted to defensive tackle this spring along with Ndulue.
OU added three freshmen defensive tackles in its 2013 signing class — Kerrick Huggins, Matthew Romar and Charles Walker — plus junior-college transfer Quincy Russell, whose academic status remains up in the air.
STAFF WRITER ADAM KEMP CONTRIBUTED TO THIS REPORT