Although I believe that RB's can (and do) get "worn down and nicked up," I find it difficult to believe that it would occur to a RB of Gurley's age IN THE FRICKEN' SUPERBOWL. Both Gurley and McVay know better than anyone else that they're not guaranteed another opportunity to play/coach on this stage. As such, I just don't see knee irritation stopping the player or coach from playing near at (or near) peak performance.
OTOH, though, I can definitely see it if Gurley wasn't part of the game plan to begin with - which (absent significant injury news) seems to be the case. Seems like a classic case of not dancing with the one who brought 'ya.