Peyton could check into successful runs in his heydey because defenses were so petrified of his ability to pass on them that they would put personnel packages on the field and line up in formations that could be exploited in the run game. Your post title suggests that if he were still on the team, this would still be the case and the Broncos would still be one of the dominant teams in the AFC, but with the rapid pace at which his arm was declining, it likely isn't. What I'm saying isn't that Peyton couldn't possibly have helped the team this year, it's that there are other issues with this incarnation of the team that could potentially keep them out of the playoffs, ones I don't think even having Manning could fix.

Personnel losses on the defensive side of the ball have made them susceptible to good rushing attacks. We didn't gash the defense on the ground just because the defense was tired due to the offense not being able to sustain drives, we did it because we have really good personnel up front and good running backs, and were getting chunk runs from the outset. And on the other side of the ball, the offensive line is clearly a problem, as is the loss of CJ Anderson. Believe me, I am well aware of how Manning made a career out of making less than stellar offensive lines and running backs look better than they were, but I don't believe it's something a 40+ year old version of him could still do. He could hardly do it last year.