It's time to fire up those backfield replacements. And there sure are plenty to go around.The injuries that have claimed several big-name players this season have opened the door for some lesser-known guys to get a shot in Week 12, just in time to be a potential factor in your league's playoff chase.My colleague, Denver-based sports writer Pat Graham, led off Tuesday's edition of "Fantasy Plays" with the case of Baltimore rookie runner Javorius "Buck" Allen, who is expected to take over with Justin Forsett lost to a broken arm.