Seattle is 15-2 in Walker's career when he gets 15 or more carries. Less than 15? 4-15. He can't be special if he's not getting the rock.
Stats like this don't really make much sense though - Walker has a whole lot of games where he has carried the ball 10-12 times for 2-3YPC. So A: we're not getting enough 1st downs or short yardage 3rd downs to keep feeding him, and B: why would you keep giving it to a guy who isn't making any yardage