This is the problem with the Mike Price type of offense UTEP runs: There isn't somebody to run the ball on third down. It's all finesse; no opponent bodies getting shoved around.
They need the "big back" in there on third down. Finding such a person, who also has speed, is ... well, he's at bigger schools. But surely the Miners can recruit a power runner or three to have on the roster.
Anyway, if I'm an opponent, and UTEP has a third and three or four, I know the Miners will be passing, and I will adjust my defense. That cuts down on UTEP chances for success.
It's a constraint that hurts the Miners.