Denver Broncos rookie running back Jonah Coleman is looking forward to joining forces with his veteran teammates at the position. Coleman suggested after the draft that he, J.K. Dobbins, and RJ Harvey will form a "three-headed monster" in the Broncos' backfield.  "Just being able to come in and be with guys like RJ Harvey, J.K. Dobbins... You ultimately have a three-headed monster in the run game," Coleman said the night he was drafted in the fourth round. "I believe that’s where it starts, in the trenches.” Coleman might be onto something. After Dobbins went down with a season-ending foot injury in Week 10, the obvious and unfortunate deficiencies in the Broncos' running back room were exposed. Fortunately, the Dobbins injury coincided with quarterback Bo Nix taking his play to the next level, which allowed the Broncos to survive the storm with Harvey as the starter, often averaging under 3.0 yards per carry.…