CATS midfielder Josh Caddy will have to prove his fitness on the training track on Thursday if he's to line up in the must-win clash with Collingwood at the MCG on Friday night.

Caddy was subbed out of the draw against St Kilda last weekend after suffering a knee injury, and he is racing to be fit to face the Magpies.

"Josh was jumping for a contest just before half-time and he felt a strain in his patella tendon," Geelong physio Mark Young said on the round 22 episode of nib Medical Room.

"That's a little inflamed, so we need to allow that to settle and we'll assess him later this week."

This week's nib Medical Room also includes Young's thoughts on:

* Mitch Duncan (calf)

* Cameron Delaney (knee)

To watch the full episode of nib Medical Room click on the video player at the top of the page