By Max Partlo
The answer to the title’s question is actually “not much”, but If you asked anyone who has ever taken a statistics class before what was going to happen to the Denver Broncos offense in 2014 after the record-setting season they had last year, you would have received a litany of responses that focused on receding to the mean, and mentioning how it would be nearly impossible for Peyton Manning and the passing game to match their record-setting performance. And, granted, the Broncos have slipped from scoring 37.9 points per game last year to only scoring 29.3  this year, even after their disappointing 7 point outing against the rams. 
Still, Manning had to recede, right? Instead, Manning’s per play efficiency has remained largely the same. His Yards per Attempt, and Passer Rating have each dipped less than 3% and 7% respectively, and are still at elite levels. The difference in the Bronco’s offensive output has actually been the decline of a run game that was at least average last year. Last year’s backfield, led by the now departed Knowshon Moreno, accumulated 1873 yards on 461 carries, for an average of 4.1 yards per carry. They also reached the end zone 16 times, and picked up 107 first downs through the ground game. This year’s rushing attack is on pace for lower totals in attempts, yards, touchdowns, and first downs, all while averaging under 3.7 yards per attempt, a figure that ranks 25th in the league.
Having Peyton Manning and an arsenal of pass catchers has helped this team run through a brutal schedule and come out in position to contend for the best record in the AFC, but there are a few telling stats that show how this inefficient attack could hamper the team as they go further. Last year, the Peyton Manning led all 16 game starters in Passer Rating, which was buoyed by his league leading performance on passes coming off of play action, where his Passer rating was 136.7. This year, Manning trails only Aaron Rodgers in Passer Rating, but his performance on play action passes is actually hurting his cause. With no play fake, Manning’s rating is a strong 110.0, good for second in the league. Yet, coming off of fakes, Manning’s rating is only 95.8. The average quarterback who has taken at least 60% of his team’s drop backs is 5.7 points higher on play action than on normal pass plays. Manning, is somehow 14.2 points worse when he fakes the handoff, which is the second largest deficit in the league. This decline in performance on play action passes is doubtlessly tied to the reduced usage of such plays in the Bronco’s offense. Last year, Manning used a play fake on 25.6% of his drops, a figure that has dropped to 20.1% this year.
Any team that has Peyton Manning is going to build their offense around the aerial attack, and hope for competency in the run game. But this year, with defenders less concerned with stopping the ineffective run game, a key part of Manning’s game has been constricted, and the overall offense has seen a subsequent dip in performance. With Montee Ball and Ronnie Hillman injured, the Bronco’s will need CJ Anderson to bear the majority of the workload in getting the run game going, and they need to, as their only three losses came on the road against strong defenses that held the Broncos to an average of 35.7 yards per game on the ground. A hall of fame quarterback solves a lot of problems for an offense, but an improved run game in Denver could help to prevent these problems, and push Manning and company back towards a record-setting pace.
 A number that would have led the league last year by a considerable margin, and is still relatively near the leading packers, who average 33 points per game.
 This one game is a very small sample compared to the whole 42 that Manning has played with the Broncos, but we can still use it to understand why this outlier occurred.
 The largest gap, surprisingly, belongs to Russell Wilson, who yields a rating of 74.9 with the fake, and 97.2 without it. Surprisingly enough, Wilson still leads the NFL in percentage of drop backs that come off of play action with 33%
 In their 7 wins, the Broncos run game has averaged 113 yards per game.