Two promising quarterbacks (Robert Griffin III and Kirk Cousins) regressed took at least temporarily in their first season playing in Gruden's offense. Gruden needs to find a solution under center and hope new defensive coordinator Joe Barry helps make a difference for the Redskins to significantly better last year's 4-12 record.
Mike Pettine, Cleveland Browns
Pettine had the Browns in playoff contention at 7-4 before the bottom fell out with five straight losses. The collapse could be a harbinger of things to come in 2015 with the NFL's worst quarterback situation and no game-breaking speed at wide receiver.
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Gus Bradley, Jacksonville Jaguars
Bradley and general manager David Caldwell inherited a train wreck of a roster when hired in 2013. Bradley's team plays hard and is well-coached defensively, but at some point soon, the Jaguars have to start winning more games after records of 4-12 and 3-13.
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Joe Philbin, Miami Dolphins
No head coach entering this season is on a hotter seat than Philbin, who is entering his fourth year in Miami without having made the playoffs. The good news: Philbin has his most talented roster to date.
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Mike Zimmer, Minnesota Vikings
Zimmer did a great job guiding the Vikings through the Adrian Peterson controversy last season and coaxing the disgruntled running back to recently return for offseason workouts. The next step for Zimmer is lifting a 7-9 team into the playoffs this season.
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Ken Whisenhunt, Tennessee Titans
He led Arizona to Super Bowl XLIII but lost 27 of 32 games in his past two seasons as a head coach for the Cardinals (2012) and Titans (2014). To regain his "Wiz" status, Whisenhunt must develop first-round pick Marcus Mariota into becoming a quality quarterback -- something that he has sorely lacked as a head coach since Kurt Warner's retirement in Arizona following the 2009 season.
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Jack Del Rio, Oakland Raiders
Jacksonville hasn't won more than four games in any season since Del Rio's departure during the 2011 campaign. Making the Raiders a credible franchise once again is Del Rio's next challenge.
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Lovie Smith, Tampa Bay Bucs
Smith could easily skyrocket back up this list in 2016, but first things first. Smith has to get the Buccaneers' ship righted after finishing an NFL-worst 2-14 in his Tampa Bay debut.
Phelan M. Ebenhack/Associated PrPhelan M. Ebenhack
21: Gary Kubiak, Denver Broncos
Here's hoping that Kubiak learned from his mistake of running too loose a ship in Houston that helped lead to his demise there as head coach.
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Rex Ryan, Buffalo Bills
After four straight seasons without a winning record or playoff appearance with the New York Jets, it's time for Ryan to actually walk the walk rather continuing to talk the talk about how good his teams will be.
Getty ImagesBrett Carlsen
Jeff Fisher, St. Louis Rams
With 19-plus seasons under his belt, Fisher has a proven track record as the second-longest tenured active head coach behind Bill Belichick. Fisher, though, hasn't posted a winning record or reached the playoffs in his past five seasons with the Rams (2012-present) and Tennessee (2009-2010). Fisher could be ready to break that personal drought with St. Louis set to field a fierce defense and potentially improved offense.
Bill O'Brien, Houston Texans
Yes, the Texans have a beastly defense led by end J.J. Watt. But not many coaches could lead their squad to a 9-7 record when forced to use four different quarterbacks because of injuries. Such a promising debut makes O'Brien a coach to watch for future greatness.
APDavid J. Phillip
Jim Caldwell, Detroit Lions
With the Lions finishing 11-5 last season, Caldwell proved he didn't need to play with Peyton Manning to flourish as an NFL head coach.
Marvin Lewis, Cincinnati Bengals
Lewis will always be remembered as the coach who helped lift the Bengals from NFL laughing stock to perennial playoff contender. However, the heat is on Lewis to help Cincinnati win its first postseason game since 1990. The Bengals are 0-6 under Lewis, including first-round losses in each of the past four seasons.
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Andy Reid, Kansas City Chiefs
From a win-loss standpoint, Reid remains one of the NFL's top coaches with a 53-43 record since 2009 with both the Eagles and the Chiefs. Reid, though, also failed to win a playoff game in three postseason appearances during that span. There are growing doubts about whether Reid still can lead a team into a Super Bowl like he did with the 2004 Eagles.
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Chip Kelly, Philadelphia Eagles
Even after consecutive 10-win seasons, there are still plenty of questions about whether Kelly's offensive philosophy can work over the course of an entire year in the NFL. The 2015 campaign should help provide answers after Kelly's radical offseason roster makeover.
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Mike McCoy, San Diego Chargers
Although the Chargers didn't enjoy a second consecutive playoff appearance in 2014, that failing was because of injuries rather than McCoy's coaching. The Chargers appear poised for another postseason run after offseason personnel acquisitions -- especially veteran guard Orlando Franklin and rookie running back Melvin Gordon -- that should allow McCoy to once again field a formidable ground attack like in 2013.
Getty ImagesRob Carr
Ron Rivera, Carolina Panthers
The fortunes of "Riverboat Ron" changed early in the 2013 campaign when Rivera became less conservative than during his first two-plus seasons on the job. The Panthers are the NFC South's first back-to-back champions since the NFL adopted its current division format in 2002. This was achieved despite general manager Dave Gettleman having to rectify the salary-cap mess left behind by predecessor Marty Hurney.
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Jason Garrett, Dallas Cowboys
Garrett was thrust into a head coaching position before he was truly ready -- midway through the 2010 season -- but has steadily grown on the job. A 12-4 record and second-round postseason appearance in 2014 proved that Cowboys players have finally bought into the coaching philosophies Garrett has been stressing.
John Fox, Chicago Bears
Detractors will point to opening playoff losses in two of Denver's past three seasons and a dreadful showing against Seattle in Super Bowl XLVIII as examples that Fox struggles to get his teams properly prepared to play at the most critical points of the season. The Bears, though, didn't wait long to name Fox their head coach earlier this year shortly after his surprising offseason dismissal in Denver. Both the Broncos and Carolina Panthers enjoyed immediate improvement after Fox joined their downtrodden franchises. Another sign of his prowess: In a league full of head-strong head coaches, Fox is flexible enough to adopt different offensive and defensive systems to best take advantage of the personnel at his disposal.
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Chuck Pagano, Indianapolis Colts
The Colts have advanced progressively further in the postseason during each of Pagano's three years on the sideline. Pagano also deserves credit for fostering an environment that has helped Andrew Luck blossom into the NFL's top young quarterback.
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Bruce Arians, Arizona Cardinals
One of life's great mysteries -- why did it take Arians until he was 60 years old to get his first full-time NFL head coaching gig? When finally given the opportunity in Arizona two seasons ago, Arians took full advantage of it. The Cardinals won 10 games in 2013 and 2014 and appear poised to make even more noise this season with a healthy Carson Palmer (knee) slated to return at quarterback.
Getty ImagesChristian Petersen
Tom Coughlin, New York Giants
The Giants have fallen on hard times the past three seasons but that is more the result of injuries and shaky personnel decisions by the front office than Coughlin's coaching. Coughlin is the only other active head coach besides Bill Belichick with two Super Bowl victories.
Sean Payton, New Orleans Saints
Clearly the greatest head coach in this franchise's history, Payton first showed his talent when leading the 2006 Saints into the playoffs in his first NFL season as the region recovered from the devastating aftermath of Hurricane Katrina. Unfortunately for Payton, his year-long NFL suspension for Bountygate in 2011 cost him a season working with quarterback Drew Brees in his prime.
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Mike Tomlin, Pittsburgh Steelers
Safe to say the Steelers know how to pick head coaches. In 2007, Tomlin became only the third coach in franchise history: Chuck Noll (1969-1991) and Bill Cowher (1992-2006) being the other two. He hasn't disappointed. Pittsburgh is 82-46 under Tomlin with one Super Bowl win and another appearance.
Getty ImagesGeorge Gojkovich
Pete Carroll, Seattle Seahawks
Carroll's third incarnation as an NFL head coach has proven his most successful. Seattle has averaged 12 wins over the past three seasons with a Super Bowl win and another appearance. Carroll, though, now faces his greatest challenge: Getting the 2015 Seahawks past the fallout of Seattle's Second-and-Dumb play call in Super Bowl XLIX that likely cost the franchise a second straight Lombardi Trophy.
Getty ImagesKevin C. Cox
John Harbaugh, Baltimore Ravens
Besides posting a 72-40 record in seven seasons with the Ravens, Harbaugh has done his best work in the playoffs. Harbaugh's 10 postseason wins rank behind only Belichick and the New York Giants' Tom Coughlin (12) among active head coaches -- and both of them have held the post for almost triple the amount of time. Harbaugh also guided Baltimore to victory in Super Bowl XLVII.
Getty ImagesDilip Vishwanat
Mike McCarthy, Green Bay Packers
In nine seasons, he has the second-highest winning percentage in the regular season (65.4) among all active coaches as well as a Super Bowl victory and four consecutive NFC North titles. While most coaches would stick to the formula that brought them such success, McCarthy deserves credit for not being complacent and realizing he may be able to do more on his end to help the Packers become even better. McCarthy ceded the offensive play-calling responsibilities this offseason to concentrate more on other areas of his team -- particularly special teams -- after last season's NFC title game collapse against Seattle.
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Bill Belichick, New England Patriots
Say what you will about Spygate or Delfategate. Those scandals cannot completely tarnish Belichick's accomplishments. No other coach in NFL history has won more Super Bowls (four, tied with Chuck Noll) or postseason games (22). And as long as Tom Brady remains as quarterback, those numbers may get even gaudier.