Quarterback is the most important position on a football field, possibly in any team sport, especially with the increasing emphasis on the passing game. Finding stability at quarterback is highly coveted in the NFL because it is considered to be integral to sustained success. Once a team believes a high-level quarterback has been found, he rarely hits the open market.

The scarcity of good quarterbacks drives teams to select passers higher than they should in the NFL draft and overpay for merely competent veteran QBs. It also leads to significant turnover because mistakes evaluating quarterbacks are constantly made. Roughly one-quarter of the 32 NFL teams will have a new starting quarterback in 2019, if recent history is any indication.

Here's a look at the passers who could be on the quarterback carousel in the offseason.

Eli Manning, Giants

The benching of Manning has seemed inevitable because the Giants are struggling to score points with the 37 year old under center. The Giants have a 1-7 record heading into this week's bye after going 3-13 last season. Head coach Pat Shurmur was noncommittal about Manning remaining in the lineup after the bye.

Manning may have gotten a reprieve for the time being because of 2018 fourth-round pick Kyle Lauletta's arrest on Tuesday during a traffic incident. Getting an extended look at Lauletta at some point to determine whether he could be the quarterback of the future makes sense given that it's already a lost season for the Giants.

Manning can't be dealt to another team in the offseason without his permission because he has a no-trade clause in his contract, which he has been unwilling to waive so far. Manning's contract runs through the 2019 season. His $17 million 2019 salary includes a $5 million fifth-day-of-the-league-year roster bonus due next March 17. It wouldn't be a shock if Manning, who has played his 15 NFL seasons with the Giants, retired rather continue his career with a new team. Without Manning on the Giants' roster in 2019, $17M of cap room would be gained.

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Jameis Winston, Buccaneers

Winston has lost his starting job (at least temporarily) to Ryan Fitzpatrick. The final straw for head coach Dirk Koetter was Winston's four-interception performance on Sunday against the Bengals, in which the 35-year-old journeyman replaced him late in the third quarter. Fitzpatrick promptly led three scoring drives to bring Tampa Bay back from an 18-point deficit to tie the score at 34-34 before Cincinnati kicked a game-winning field goal as time expired.

Winston has regressed since returning from the three-game suspension he served at the beginning of the season under the league's personal conduct policy for allegedly groping a female Uber driver in March 2016. The alleged incident was a reminder of Winston's off-the-field behavior while at Florida State, which included a sexual assault accusation. Fitzpatrick, who was named NFC Offensive Player of the Week in each of the first two weeks after leading the Buccaneers to upset wins over the Saints and the defending Super Bowl champion Philadelphia Eagles, is outplaying Winston this season .

Winston has thrown 10 interceptions, tied for the most in the NFL, in only 13 quarters of game action this season. Winston also has league-high 6.8 percent interception rate.

The 2015 first-overall pick is scheduled to make $20.922 million in 2019 since the Buccaneers picked their option for a fifth year. The option was guaranteed for injury upon exercise. It becomes fully guaranteed on the first day of the 2019 league year, which is next March 13. Winston's play this season in addition to his off-the-field transgressions present a good case against him getting a fifth year in Tampa. The Buccaneers would no longer be on the hook for the $20.922 million by releasing a healthy Winston prior to the 2019 league year starting.

Joe Flacco, Ravens

The Ravens put Flacco on notice by taking 2016 Heisman Trophy winner Lamar Jackson with the last pick in the first round of this year's draft. Flacco has been a slightly above average quarterback at best in the five and half seasons since being named Super Bowl XLVII MVP. His stellar play during the 2012 playoffs led to him briefly becoming the NFL's highest-paid player in 2013. The Ravens have been to the playoffs only once since their Super Bowl XLVII win. Missing the playoffs for a fourth-straight season could prompt the Ravens to turn to Jackson next year. 2019 is the first year the Ravens can move on from Flacco's contract without adverse salary-cap consequences, although his $26.5 million cap number is tied for the seventh highest in the NFL. The Ravens would have a $16 million cap charge in 2019, a $10.5 million cap savings, by releasing or trading Flacco next offseason.

Derek Carr, Raiders

The dismantling of the Raiders by head coach Jon Gruden, the main power broker within the organization, has prompted speculation that Carr will be in a different uniform next season, although he has reportedly been given assurances he is the team's quarterback for the foreseeable future. Gruden has a reputation for being extremely demanding of his quarterbacks and souring on them quickly. Surprisingly getting a first-round pick from the Cowboys for wide receiver Amari Cooper could lead to the Raiders demanding a king's ransom in order to deal Carr, who tied for third in the MVP voting two seasons ago.

The remaining four years of the five-year, $125.025 million contract extension Carr signed in June 2017 to become the league's first $25 million-per-year player are extremely affordable given the recent explosion in quarterback salaries. Carr is under contract through the 2022 season for just over $78.5 million. The Raiders would pick up $15 million of 2019 cap room by trading Carr next offseason. There would be $7.5 million in dead money, a cap charge for a player no longer on the roster, relating to the signing bonus proration from Carr's 2019 through 2021 contract years.

Blake Bortles, Jaguars

The Jaguars' decision to go all in on Bortles this season after an unexpected playoff run to the AFC Championship Game seems to be backfiring. Bortles was given a two-year, $34.497 million extension (worth up to another $12.5 million through salary escalators and incentives) with $26.5 million fully guaranteed instead of him playing the 2018 season on his $19.053 million fifth year option.

Bortles was benched for backup Cody Kessler early in the third quarter of the Jags' Week 7 loss to the Texans. He has remained Jacksonville's starting quarterback, but head coach Doug Marrone has him on a much shorter leash.

Bortles has taken a step backwards after being an effective game manager in 2017. He is completing 55.7 percent of his passes (78 of 140) for 926 yards while throwing just three touchdowns with five interceptions to post a 68.3 passer rating during Jacksonville's current four-game losing streak, which is putting a return trip to the playoffs in jeopardy.

The Jaguars would have been able to walk away from Bortles after this season without any cap consequences if he were still playing under his fifth-year option. Because of the extension, the Jaguars could have as much as $16.5 million in dead money by releasing Bortles during the offseason. This stems from his $6.5 million salary guarantee in 2019, which has an offset, and $10 million of signing bonus proration from his 2019 and 2020 contract years. Bortles' $16 million and $18 million salaries in the next two years, as well as his inconsistency, limit his trade value.

Ryan Tannehill, Dolphins

2017 was going to be a critical year for Tannehill's future in Miami because he hadn't consistently lived up to being the eighth-overall pick in the 2012 draft before he re-injured his left knee during the preseason. Tannehill originally hurt his knee late in the 2016 season. He missed 2017 after surgery to repair the ACL in his knee. Fortunately for Tannehill, Miami didn't bring in any serious competition at quarterback through free agency or the draft. An injury to Tannehill's throwing shoulder has kept him out the last three games. His return to the lineup is uncertain.

It may be time for the Dolphins to start looking for a more reliable quarterback, partially because of Tannehill's durability concerns. Tannehill has the NFL's sixth-largest 2019 salary cap number at $26,611,666. The Dolphins would pick up $13,188,332 of cap space by parting ways with Tannehill next year. It would have been $18.75 million of room if the Dolphins hadn't restructured Tannehill's contract for cap purposes during the offseason.

Nick Foles, Eagles

The Eagles held onto Foles as insurance in case Carson Wentz had a slow recovery from tearing multiple ligaments in his left knee late last season instead of dealing him when his trade value was at its peak. Foles didn't play at the same level as in last season's playoffs, when he earned Super Bowl LII MVP honors during the two games he started this season before Wentz's return. Nonetheless, Foles' Super Bowl pedigree should provide him an opportunity to be a starter in 2019.

Tyrod Taylor, Browns

The Browns didn't trade a 2018 third-round pick to the Bills for Taylor to be the long-term solution at quarterback. This became abundantly clear when the Browns used the first-overall pick in this year's draft on 2017 Heisman Trophy winner Baker Mayfield. Taylor sustaining a concussion in Week 3 against the Jets opened the door for Mayfield to take his job sooner than expected. Mayfield led the Browns to their first victory since Week 16 of the 2016 season in relief of Taylor. A benching was eventually going to happen. Taylor was completing only 48.8 percent of his passes for 462 yards and had a 63.7 passer rating as the starter. He was serviceable but unspectacular during the previous three seasons as Buffalo's starting quarterback.

Teddy Bridgewater, Saints

The gruesome, career-threatening knee injury Bridgewater suffered during the 2016 preseason as the Vikings starting quarterback was responsible for a soft market in free agency. Bridgewater signed a one-year, $6 million contract with the Jets (worth up to $15 million through incentives) containing only $500,000 guaranteed. He raised his stock considerably in the preseason by beginning to display his pre-injury form after missing the better part of two seasons. The Jets got a 2019 third round pick from the Saints for Bridgewater in a preseason trade. It's hard to imagine a scenario where Bridgewater is with the Saints next year unless Drew Brees, whose contract runs through the 2019 season and isn't showing any signs of slowing down at 39, is ready to hang up his cleats. Bridgewater is likely to find some team willing to give him a chance to at least compete for a starting job next season.

Marcus Mariota, Titans

Mariota's progress stalled in former head coach Mike Mularkey's "exotic smashmouth" offense. New offensive coordinator Matt LaFleur helped 2016 first-overall pick Jared Goff make tremendous strides in 2017 while serving in the same capacity with the Rams. He has yet to have similar results with Mariota, who has been slowed by an elbow injury to his throwing arm and the loss of his top two receiving threats from last year. Tight end Delanie Walker suffered a season ending ankle injury in the first game. Wide receiver Rishard Matthews asked for his release a couple of weeks later because of a lack of playing in his return from preseason knee surgery. The Titans could delay a decision on Mariota by giving him the benefit of doubt in 2019 with his $20.922 million fifth-year option while hedging their bets with the selection a quarterback relatively early in next year's draft.

Case Keenum, Broncos

The Broncos haven't gotten the Keenum who helped the Vikings win the NFC North last season with a 13-3 record, which tied for best in the NFL, en route to an NFC Championship Game appearance, following starting quarterback Sam Bradford's early-season knee injury. His 2017 performance is looking like an anomaly. Keenum threw seven interceptions last season. It took him six games this season to exceed that number. Keenum's 10 interceptions are tied for the most in the league. His 63.9 completion percentage and 83.0 passer rating are 23rd and 26th respectively in the NFL. Keenum still has the confidence of Broncos president of football operations and general manager John Elway despite the turnovers. That might change if Denver, which has a 3-5 record, doesn't start turning the season around. Keenum having $7 million of his $18 million 2019 base salary fully guaranteed wouldn't necessarily prevent Elway from finding a new quarterback for next season.