How come Pierre Thomas averages 4.9 yards per carry?

Reggie Bush is watched when ever he is on the field because of his speed, if you let him open for a second he will do what he did to the Bears in the playoffs. Pierre Thomas just doesn't have that kind of play making ability so defenses don't pay that much attention to him. Steve Slaton is fast while older Texans running backs were slow. Also, he has a lot of big runs that bring up his average.