What's the deal with Washington playing Dillon Johnson so much?

I understand he's a senior and has been one of the better backs this year, but dude was running on one ankle all night.

He couldn't cut like he normally does and you could just tell he didn't have it. Wasted 13 touches on him tonight

Looks like it's being reported that he has a high ankle sprain too

I know it's hard to keep the kid out but this is the National Championship, you cannot run out a player that would be detrimental to you winning it.