As anyone who's played even HS football knows, you're never 100%. The sprains, dislocations, fractures, abrasions, pulls, strains, tears, etc. are innumerable. By the time you're a couple games into the season, the only guys who aren't dinged up in some way or another are practice players that don't try all that hard...
College players are fierce competitors, they're used to playing hurt, and they have waited their entire lives for their moment—which often never comes, or comes and goes in a flash.
I'm confident that Rose was in the game because HE wanted to be in the game. People who immediately jump to "Whitt the slave-driver, forcing players to play hurt" have no idea what this means to the players themselves, and are either (i) DEEPLY biased by their hate for the UofU or (ii) just don't understand how much it means to finally get a starting opportunity.
We talk about "giving our left hand" for this or our that—and for most us, that's figurative—but every weekend we watch teens and young men who take that in a very literal sense.