After a tumultuous 2015, the Miami Dolphins, the AFC East's fourth-place finisher, have a lot of thinking to do about their future -- particularly as it pertains to quarterback Ryan Tannehill.

Tannehill received an extension just last year, but for reasons outlined below, 2016 will have a huge impact on Tannehill's future not only with the Dolphins but possibly as a starting quarterback in the NFL.

Turmoil hit the Dolphins hard after a big offseason that saw them land major talent on both the offensive and defensive side of the ball.

Kenny Stills and Jordan Cameron should have helped elevate the Dolphins' offense. But after a 1-3 start that saw the Dolphins fail to score more than 20 points in any game, head coach Joe Philbin was sacked and replaced with Dan Campbell.

That firing perhaps caused a "dead cat bounce" -- with the Dolphins stringing together two wins in a row in Campbell's first two games as head coach. That would, incidentally, be the Dolphins' longest winning streak of the season.

Further, news of inner locker room turmoil began to surface, "highlighted" by cornerback Brent Grimes' wife Miko tweeting insults directed at Tannehill.

Tannehill, for his part, did not do much to assuage fears -- reportedly insulting practice team players earlier this year. Soap opera aside, the on-the-field production from Tannehill left a ton to be desired, and that's really what matters both immediately and in the long term.

Mediocre at Best

Our signature metric at numberFire is Net Expected Points (NEP). It's explained in the great detail elsewhere, but these are the basics: the guaranteed $21.5 million is essentially spread over 2015 and 2016. 2017 has a small $3.5 million guarantee if Tannehill is on the roster for what amounts to a nominal amount of time.

In other words, while Tannehill's money is guaranteed whether he's on the roster in 2016 or not, no other significant money is guaranteed to Tannehill.

After 2016, Tannehill's cap number increases from $11 million in 2016 to over $20 million in 2017, where it will more or less remain steady for the life of the deal. Each year of the deal is essentially a year-to-year option for the Dolphins, so in theory, they could cut ties after 2017 or 2018 -- until the deal is up in 2020 -- if they feel that Tannehill ever becomes not worth the hit. 

That said, it's most likely that Dolphins' brass will make their decision after the 2016 season, before the cap hit nearly doubles.

Since the money is not guaranteed, the Dolphins will be able to cut ties basically obligation-free after this year.

With a new regime inbound to Miami, it's very likely 2016 will be a year under the microscope for Tannehill, as the organization will need to decide whether he's worth the $20 million owed in 2017.

New head coach Adam Gase is expected to work closely with Tannehill -- and have full control over the 53-man roster.

Is It Tannehill Alone?

We haven't been terribly kind to Tannehill here, but he's not the only problem.

The Dolphins spent a ton of money on the defensive side of the ball, making a splash with free agent Ndamukong Suh. Suh was supposed to help the Dolphins become a dominant rushing defense -- and he did to an extent. The Dolphins were the 21st best team in terms of Adjusted Defensive Rushing NEP per play in 2014. They moved up to 15th in that same metric this year. 

Miami's passing defense, however, was the 31st ranked unit in Adjusted Defensive Passing NEP per play in 2015, a huge slide from 19th, which is where they finished in 2014.

As a result, Miami, our 19th best overall defense in 2014, took a massive step backwards into 30th place this year. At the end of the day, the huge slide in defensive output is a huge component of the Dolphins' disappointing 2015 campaign.

Additionally, the Dolphins' rushing unit was poor in 2015 as well. In Adjusted Rushing NEP per play, Miami ranked 21st.

Now, that may partially be due to Tannehill's lack of effectiveness -- a team may be willing to stack the box against the Dolphins' run knowing that they could handle Tannehill. Likewise, the opposite may also be true -- that an ineffective rushing attack allowed defenses to key in on Tannehill and focus on stopping the pass.

We cannot really know whether it's the chicken or the egg here, but the rushing attack did not exactly help the Dolphins' cause this year.

Conclusion

Tannehill will spend 2016 firmly under the Dolphins' microscope.

There's been improvement when considering schedule strength, but it hasn't been enough to justify his ballooning salary. 

2015 had to be disappointing for Miami fans, and while Tannehill was unspectacular at quarterback, no unit was really improved at all outside of their rushing defense via the addition of Suh.

A huge slide in their passing defense made this a bottom-three defense overall, and it's hard to blame Tannehill for that.

That's not to let Tannehill off the hook -- there are certainly some mitigating factors throughout this team that need to be considered. This offseason will be instrumental as to whether the Dolphins as a whole can improve enough to secure Tannehill's position after 2016.