SOUTH BEND, Ind. (AP) — Notre Dame coach Brian Kelly isn't sure who will be starting at every defensive position for the 24th-ranked Fighting Irish against Pittsburgh because he's not sure who is available.

Kelly was still waiting Sunday to get MRI results from nose guard Louis Nix III, who missed the past two games with knee tendinitis and a small meniscus tear. His replacement, Kona Schwenke, is out with a high ankle sprain sustained late in the 38-34 win against Navy.

Backup linebacker Ben Councell sustained a season-ending knee injury. Starting defensive end Sheldon Day aggravated a high ankle sprain against Navy and may be ready to play.

Starting safety Austin Collinsworth sustained a strained neck against Navy and will undergo an MRI on Monday.