Everything starts with the quarterback in today's NFL. Sustained NFL success is difficult without good quarterback play, although the Broncos won Super Bowl 50 because of a suffocating defense.

The search for the ever-elusive franchise quarterback drives some of the NFL's most important transactions. For example, the Rams and Eagles gave up multiple draft picks to move up to the first and second spots in the 2016 NFL Draft to take Jared Goff and Carson Wentz. Brock Osweiler got a four-year, $72 million deal containing $37 million fully guaranteed after seven career starts. This is because demand outweighs the supply of high-level quarterbacks in the NFL.

Here's a look at the players that could be on the quarterback carousel in the offseason.

A general principle in sports is players don't lose starting jobs because of injury. Despite this notion, many believe 2016 fourth-round pick Dak Prescott should remain at quarterback because of his surprising play in the Cowboys' 5-1 start to the season.

It remains to be seen whether owner Jerry Jones gives the reins back to Romo in the coming weeks when he's ready to return from the fractured bone in his back that has sidelined him since late in the preseason. Prescott is clearly the Cowboys' quarterback of the future regardless of the decision, which means Romo's days in Dallas could be numbered sooner rather than later.

Dak Prescott is the future in Dallas. USATSI

It wouldn't be a surprise if Dallas traded the 36-year-old Romo in the offseason. Because of his age and injury history, the Cowboys might not be able to get more than a mid-round draft pick for Romo, who has three years left on his contract after this season for $54 million.

Romo has the NFL's biggest 2017 salary cap number at $24.7 million. Trading Romo would leave Dallas with a $19.6 million cap charge next year because of the signing bonus proration from his 2013 contract extension and subsequent contract restructures in 2014 and 2015 for cap purposes.

Kaepernick reworking his contract helped paved the way for him to reclaim the starting job he lost to Blaine Gabbert last season. Gabbert was ineffective in this season's first five games. The last three years of Kaepernick's contract (2018 through 2020) worth $58 million were eliminated in the renegotiation. More importantly, the injury guarantee from Kaepernick's $14.5 million base salary was also removed so the 49ers won't be on the hook for the money if he sustains a serious injury.

Kaepernick has the option to void his 2017 contract year before the start of the 2017 league year. Starting to regain the form he displayed before his career began a downward spiral in 2014 would give him a tremendous amount of leverage with the 49ers. Kaepernick can't be franchised in the offseason because his voiding period starts after the tag designation period ends. The most likely scenario is the 49ers and Kaepernick parting ways after the season where $16.9 million of 2017 salary cap room is gained by not having his $19,365,753 cap number on the books.

Kaepernick's refusal to stand for the national anthem before games to protest racial injustice could impact the demand for his services if he's on the open market next offseason, presumably looking for an opportunity to compete for a starting job. Top backup quarterback money to compete for a starting job is currently $7 million to $7.5 million per year with incentives and salary escalators that could make a two- or three-year deal as much $12 million per year.

The guaranteed money in Cutler's contract is the primary reason he remained in Chicago when head coach John Fox and general manager Ryan Pace took over in 2015. The guarantees made trading Cutler virtually impossible and releasing him unpalatable.

These concerns no longer exist after the season because there won't be any guaranteed money left in Cutler's contract. Fox's refusal to commit to Cutler once he recovers from a sprained thumb, which has kept him out of action since the second game of the season, suggests that the long-time starting quarterback is on his way out of Chicago. Brian Hoyer has been steady in Cutler's absence.

Jay Cutler's days in Chicago appear to be numbered. USATSI

It's hard to imagine there will be a team willing to take on the last four years of Cutler's contract for $72.7 million in the offseason through a trade. Whether it's through a trade or release, the Bears will gain $14 million of cap room from removing Cutler's $16 million 2017 cap number from their cap equation.

Cousins playing on his $19.953 million non-exclusive franchise tag was a no brainer considering Washington's reported best offer was $16 million per year with $24 million in guarantees. The Redskins aren't any closer to knowing whether Cousins is worthy of a substantial long-term financial commitment six games into the 2016 season because of inconsistency he didn't display during the second half of the 2015 season.

Cousins completed 73.6 percent of his passes for 2,212 yards with 19 touchdowns and two interceptions to post a 126.1 passer rating over the final eight regular season games in 2015. He had the highest completion percentage and the third-best passer rating during a second half of a season since the turn of century.

Getting to the playoffs for a second straight season with Cousins could force the Redskins to franchise him again next year for $23,943,600 absent a long-term deal before early next March. That's especially true if Falcons offensive coordinator Kyle Shanahan -- Cousins' former play caller in Washington -- gets a head coaching job after the season and comes calling. If Cousins' uneven play continues, his realistic worst-case scenario should be getting a deal similar to Brock Osweiler's four-year, $72 million deal with the Texans, given there are more NFL teams than competent starting quarterbacks.

Adam Gase is giving Tannehill a long leash despite his early-season struggles. The new head coach recently declared that Tannehill -- the No. 8 pick in the 2012 draft -- will stay in the lineup for the rest of the season. He placed part of the blame for Tannehill's performance on poor offensive line play.

Will the Dolphins move on from Ryan Tannehill after the season? USATSI

It's conceivable that the Dolphins could look to trade Tannehill in the offseason if he doesn't turn the rest of the season into a true breakout performance. Only $3.5 million of Tannehill's $17.975 million 2017 base salary is fully guaranteed. The remaining $14.475 million becomes fully guaranteed in mid-March on the fifth day of the 2017 league year. A reunion with Cutler, who should be available, wouldn't be out of the question if Gase is looking for a new quarterback. Cutler thrived in 2015 with Gase during his lone season as the Bears' offensive coordinator.

Garoppolo was passing his test as a starting QB with flying colors before spraining the AC joint in his right shoulder two games into Tom Brady's four-game Deflategate suspension. He had connected on 42 of 60 passes (70 completion percentage) for 496 yards with four touchdowns and no interceptions.

Garoppolo's success creates an interesting dilemma for the Patriots in the offseason since 2017 is his contract year and Brady, who is under contract through the 2019 season, isn't showing any signs of slowing down at 39. At a minimum, the Patriots would likely be able to get similar compensation for Garoppolo in a trade that the Eagles received from the Vikings for Sam Bradford when Teddy Bridgewater went down. The Eagles got a first-round pick and a fourth-round pick that can elevate to the third or second round under certain conditions. The acquiring team would likely insist on signing Garoppolo to a long-term deal in the process, presumably in the Brock Osweiler neighborhood.

Some team is going to pay Jimmy Garoppolo big bucks to be the starting QB. USATSI

Letting Garoppolo play out his contract and franchising him in 2018, which could be in the $23 million neighborhood, with the purpose of trading him or Brady could also be an option since Father Time is undefeated. The Patriots sent quarterback Matt Cassel (and Mike Vrabel) to the Kansas City Chiefs for their 2009 second-round pick after franchising Cassel in 2009.

The Bills gave Taylor a $7.5 million raise this season for an option, which must be exercised by the third day of the 2017 league year on March 11. Buffalo will let Taylor's play this season determine whether he's worth an additional five years for $82.5 million (worth up to $101.75 million through salary escalators and incentives). Taylor has emerged as one of the NFL's best dual-threat quarterbacks since becoming a starter at the beginning of last season. The biggest obstacle to Taylor remaining in Buffalo is a collapse by the team resulting in head coach Rex Ryan and/or general manager Doug Whaley being fired. A new regime could look to bring in a traditional pocket passer instead of picking up Taylor's option.

Fitzpatrick's lackluster play in the Jets' disastrous 1-5 start to the season prompted head coach Todd Bowles to bench him for Smith, a 2013 second-round pick who started 29 of the 30 games he played in his first two NFL seasons. After receiving a one-year, $12 million contract right before the beginning of training camp, Fitzpatrick has thrown an NFL-high 11 interceptions this season. He is also last in the NFL in quarterback rating (63.4) and completion percentage (57.0). In all likelihood, Fitzpatrick is destined to be a backup for the remainder of his NFL career.

Smith, who is in his contract year, gets another chance to prove to the Jets that he's the long-term answer at quarterback. If Smith falters, 2014 fourth-round pick Bryce Petty would likely be next in line.

Assuming the Jets become convinced that their 2017 starting quarterback isn't currently on the roster, making an attempt to acquire Romo may be a possibility in the offseason since they are a veteran team built for the present. Fitting in Romo's $14 million 2017 salary would require some salary cap gymnastics because Jets have $168.9 million in 2017 cap commitments with 48 players under contract and hardly any cap room to carry over from this season.

Robert Griffin III had found a good situation to try to resurrect his career until landing on injured reserve (IR) because of fracturing a bone in his left shoulder during the season opener. He is eligible to return to action from IR on November 10 against the Baltimore Ravens.

It may make more sense to leave him on IR since other quarterback injuries have pressed Cody Kessler, a third-round pick this year, into action and the Browns appear to be in the hunt for the first overall pick in the 2017 draft. The Browns can walk away from the two-year, $15 million deal (worth up to $22 million with incentives) Griffin signed in the offseason with only a $1.75 million 2017 cap charge from his $3.5 million signing bonus.

A career game by Keenum against the Detroit Lions in Week 6 where he completed a franchise-record 19 straight passes is helping delay the inevitable switch at quarterback to 2016 first-overall pick Jared Goff. If Keenum, who was given the seldom-used first-round restricted free agent tender ($3.635 million for 2016), can't find a situation in the open market next offseason to a compete for starting job, re-signing with the Rams for top backup money on a Chase Daniel type deal may be appealing. The Eagles signed Daniel to a three-year, $21 million deal (worth up to $36 million through base salary escalators and incentives) with $12 million fully guaranteed in March.