Our 2015 NFL preview series ranks every team, from worst to first. Today: the No. 21 Bills.

2014 Record: 9-7

Head coach: Rex Ryan

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Key arrivals: LeSean McCoy (running back), Charles Clay (tight end), Percy Harvin (wide receiver), Tyrod Taylor (quarterback), John Conner (fullback), Alex Carrington (defensive end)

Key departures: Scott Chandler (tight end), Kiko Alonso (linebacker), C.J. Spiller (running back), Lee Smith (tight end), Chris Hairston (offensive tackle), Da'Norris Searcy (safety)

2015 Schedule:

Sept. 13: Indianapolis, 1:00 pm

Sept. 20: New England, 1:00 pm

Sept. 27: at Miami 4:25 pm

Oct. 4: New York 1:00 pm

Oct. 11: at Tennessee 1:00 pm

Oct. 18: Cincinnati 1:00 pm

Oct. 25: at Jacksonville 9:30 am

Nov. 1: BYE

Nov. 8: Miami 1:00 pm

Nov. 12: at New York Jets 8:25 pm

Nov. 23: at New England 8:30 pm

Nov. 29: at Kansas City 1:00 pm

Dec. 6: Houston 1:00 pm

Dec. 13: at Philadelphia 1:00 pm

Dec. 20: at Washington 1:00 pm

Dec. 27: Dallas 1:00 pm

Jan. 3: New York Jets 1:00 pm

TRAINING CAMP QUESTION: Can the Bills avoid having the worst starting quarterback situation?

The scenario is all too familiar for a Rex Ryan-coached team. Everything is in place for the Bills to make a strong playoff push except the game's most important position. The offseason struggles of Matt Cassel, Tyrod Taylor and E.J. Manuel are understandable considering the defensive talent and creativity Buffalo's offense was facing during practice. But it would have been nice to see any member of the trio begin to separate themselves from the pack. Since that didn't happen, expect an open competition in training camp with Cassel and Taylor having the best odds to win the job.

IF EVERYTHING GOES RIGHT:

Ryan and offensive coordinator Greg Roman's plan is executed to perfection and the Bills have a stifling running game mixed with an efficient passing attack. The defense certainly should be one of the very best in the league. One prominent scout told FOXSports.com that if the Bills win less than 10 games, it would be widely considered a failure.

IF EVERYTHING GOES WRONG:

The Bills have trouble pinpointing who their quarterback is and are forced to have a turnover machine under center. While most of the offense should be built around LeSean McCoy, if the former Philadelphia Eagle were to sustain any type of injury it would severely damage Buffalo's expectations.

BREAKOUT PLAYER: Wide receiver Sammy Watkins

Watkins faded during the second half of his rookie campaign and suffered a hip injury that required offseason surgery. Although uncertainty remains at quarterback, the Bills signed some high-end skill-position talent this offseason to complement Watkins as he tries to prove worthy of being the first wide receiver drafted last year ahead of Odell Beckham Jr.

CIRCLE THIS DATE ON THE CALENDAR GAME: vs. New England in Week 2 (1 pm ET/September 20)

Even if Patriots quarterback Tom Brady is suspended, defeating New England would be a huge step for a Bills squad that has won just two of the past 22 meetings (including Week 17 last year where the Patriots rested their starters).

ALEX MARVEZ'S PREDICTION: 8-8, fourth place

You know the expression that insanity is when you keep doing the same things over and over again expecting different results? This applies to new Ryan. After ineffective quarterbacking helped torpedo his tenure with the New York Jets, one would think Ryan should have made addressing the position his top priority after arriving in Buffalo.

Instead, the Bills enter training camp without a clear-cut starter or even backup. Ryan must hope that: A) Matt Cassel regains his 27-touchdown, seven-interception form from the 2010 season; B) Tyrod Taylor was a hidden gem sitting as Joe Flacco's backup the past four years in Baltimore; or C) E.J. Manuel's NFL career can be salvaged.

Whoever wins the job will have a strong supporting cast led by running back McCoy, tight end Charles Clay, and wide receivers Percy Harvin, Sammy Watkins and Robert Woods. Plus, the Bills don't need the next Jim Kelly under center to win. A game-manager who avoids excessive turnovers should be sufficient considering the monster of a defense that Ryan is preparing to field. Every member of the front four that helped the Bills register an NFL-high 54 sacks in 2014 has returned.

As the offense finds its groove under new coordinator Greg Roman, Buffalo will need the defense to carry the team early in the season with a schedule that features opening games at home against Indianapolis and New England followed by a Week 3 road trip to Miami.