The red zone on a football field is arbitrary. Why shouldn't it start at the 10-yard line? The 15? The 25?

Since this subjectivity exists, it's not exactly the most mathematical way of proving whether or not a player is good when it counts. Any person who analyzes the game with numbers understands this.

But fans and analysts have accepted this area of the field as special, putting a stronger emphasis on play when a team reaches an opponent's 20-yard line. 

This is especially true of quarterback play.

Often, folks will look at simple counting statistics like touchdowns and interceptions to judge how well a quarterback performs, both outside and inside the red zone. If you come to numberFire.com a lot, though, then you'll know we're not just about that. Because those numbers don't tell the entire story.

We use a metric called Cam Newton this season. Though Marcus Mariota surprisingly had the same per drop back efficiency -- and a much higher Success Rate, which measures the percentage of positive plays made by a player -- Newton's 46.09 Passing NEP total trumps Mariota since the Titans' passer was unable to finish the year. 

The most efficient quarterback in the NFL this year on a per drop back basis, according to our numbers, was Andy Dalton. He had a 0.35 Passing NEP per drop back rate. That means an average Dalton throw -- or Carson Palmer, who was oh-so-close to Dalton's efficiency -- was still 42% less effective than a toss from Newton or Mariota in the red zone this season. That's ridiculous.

Oh, and by the way, this chart doesn't include Cam's rushing. Meaning he was this good with just his arm. 

CaMVP.

The only surprising quarterback on this list aside from Mariota is Blaine Gabbert. I can promise you that our computers didn't malfunction -- Gabbert was actually a baller close to the end zone. On 30 attempts, he completed 21 passes for 8 touchdowns and 0 picks.

Funny enough, the absolute worst quarterback in the red zone this season was Colin Kaepernick, who averaged -0.41 Passing NEP per drop back within his opponents' 20-yard line. That's nearly a full point difference on each pass compared to his teammate.

Lastly, I do want to talk about Blake Bortles, who many would probably expect to be on this list. After all, only Tom Brady threw more red zone touchdowns than him this year.

Well, Bortles also attempted the most passes in the red zone -- tied with Aaron Rodgers -- in the NFL this year. In other words, he had more opportunities to throw touchdowns than almost every other quarterback. 

He also took a lot of sacks. Though not all of them were his fault, only Eli Manning lost more Net Expected Points in the red zone from sacks than Bortles.

And let's not forget that one of his red zone picks was really costly. If you recall, it came against the Falcons, where they took a throw from the 1-yard line 84 yards in the opposite direction. Clearly, if you've got your head wrapped around NEP, that's a big deal. And Bortles was dinged by that play.

In the end, Bortles still was a middle-of-the-road passer in the red zone -- not a low-end one. We'll take a look at those players next.