NFL

How Improbable Was Denver's Thursday Night Football Comeback?

JJ Zachariason  —  @LateRoundQB Sep 18th, 2015
Peyton Manning and the Broncos looked lost through a quarter and a half of play last night, but then everything changed.

Peyton Manning is done.

That, at least, is what social media wanted us to think during the first half of Thursday night's tilt between the Broncos and Chiefs.

It's a time for overreaction in the NFL, and that's precisely what happened. After a pick-six in the second half of the second quarter, Manning's Broncos were down 14-0, with just a 13.45% chance to win the contest according to numberFire Live. At the time, Manning's Passing Net Expected Points (NEP) total was -11.53, meaning a league-average quarterback would have swung the game -- to that point -- in favor of the Broncos by nearly 12 points. And that doesn't even consider that league-average passers are more efficient than "zero". In actuality, Manning was playing about two touchdowns below expectation up to that point in the game.

Little by little, though, Manning climbed back. After tossing a touchdown pass to Emmanuel Sanders with just over two minutes to go in the first half, the Broncos had a shot -- albeit a small one -- to win the game with 21.61% win odds.

But the half wasn't exactly over for Denver. Aqib Talib picked off Alex Smith, putting the Broncos in favorable field position. Manning then connected with Virgil Green at the end of the half, bringing the Broncos' win probability to a solid 42.88%. In other words, from Manning's interception for a touchdown with under seven minutes to go in the second quarter through the end of the second quarter, the Broncos went from having 13.45% odds of winning the contest to 42.88%. 

Fast forward to the fourth quarter. The game is tied 17-17 after both teams hit field goals in the second half. The Chiefs are in the red zone, and backup running back Knile Davis scores a touchdown with under two-and-a-half minutes to go. When an unsportsmanlike penalty against the Broncos is added to this score, the Chiefs had a 97.68% chance to win the game (this was then dropped to 91.09% after the kickoff).

Denver had one shot, and Manning made the most of it. The 11-play, two-minute long drive tied the game up for Denver, and with a little over 30 seconds to play, the game looked to be going into overtime. And our numbers still had the Chiefs as roughly 58 percent favorites given they were playing at home as favorites in the game.

A Jamaal Charles fumble changed all of that. The Chiefs could have simply taken a quarterback kneel to force overtime, but they opted to run Charles on first down. He fumbled, Bradley Roby picked it up and ran it in for a score, and the rest is history.

Not surprisingly, the Charles fumble forced the biggest swing in last night's game -- Kansas City had a win probability of 57.61% when the offense took the field at the end of the fourth quarter, and the fumble dropped that total by 54.38%.

Here's a look at the change in win probability throughout the game, courtesy of numberFire's Twitter account.

If you're wondering, Manning still ended the contest with a Passing NEP of -1.08, which is brought down by his costly interception that went for a touchdown. But his play was still about eight points better than Alex Smith's, who accumulated a -9.02 Passing NEP on his 25 drop backs.

And if we look strictly at what happened to Manning after that interception, then, well, I think it's safe to say Manning isn't done quite yet.