[sportscurmudgeon]

GMScud:

Agree completely that a knee injury would be a whole lot worse than a hip flexor. So would an ankle or an Achilles tendon injury... But a hip flexor injury can - when it is favored even a little bit - lead to another minor injury and those things can then begin to pile up.

I'm not saying that WILL happen, but running backs have enough opportunities to incur injuries without adding a weakness in the hips/legs - - which is where they make their living.