NFL depth chart 2015: Quarterback and running back highlight Bills’ camp battles

Despite notching their first winning season in more than a decade, the Buffalo Bills missed the playoffs for the 15th straight year in 2014. At the end of the season, it was clear that the team needed to make a huge splash this winter in order to snap the league's longest active postseason drought and bring some excitement to a bored fan base in western New York.

The hiring of Rex Ryan in early January was the perfect shot of adrenaline for this franchise, a player's coach who would add a swagger and confidence to a team desperate to remake its football culture. Ryan inherited an elite defense, so it was hardly a surprise that the majority of the team's offseason moves focused on improving an offense that ranked 18th in points scored and 26th in total yards last year.

With Ryan at the helm and Greg Roman as offensive coordinator, the Bills filled out the roster with players capable of thriving in a smashmouth offensive system. The biggest move was trading for LeSean McCoy, a workhorse back who has accumulated the most carries and second-most rushing yards of any player over the past two seasons.

They also added some weapons on the outside with the signings of free agent wide receiver Percy Harvin and transition-tagged tight end Charles Clay, both of whom should bring much-needed versatility to the Bills' ground-and-pound offense. The quarterback situation was further muddled with the addition of veteran Matt Cassel, who was mediocre as a starter in nine games for the Vikings in 2013 and 2014.

Without a first-round pick, the Bills were not in position to draft a super-impact player, and instead focused mostly on adding depth to the offensive side of the ball. Although most of the experts gave the Bills poor grades for their draft class, they did potentially get a few late-round gems in running Karlos Williams (fourth round), tight end Nick O'Leary (sixth round) and wideout Dezmin Lewis (seventh round).

The Bills passed on drafting a signal caller last week, and will apparently go to camp with the four quarterbacks on the spring roster: Cassel, EJ Manuel, Tyrod Taylor and Jeff Tuel. Ryan has made it clear that there is no surefire incumbent starter and that there will be an open competition for the No. 1 job this season.

Cassel likely has the leg up at this point as the most experienced player, but he's done little in the past few years to show that he deserves to be a starting quarterback. Since leading the Chiefs to the playoffs in 2010, Cassel is just 9-17 and has the fourth-worst passer rating (74.0) of the 43 quarterbacks in that span with at least 500 attempts.

McCoy is clearly the No. 1 back in Buffalo, but it is anybody's guess how the rest of the depth chart will shake out. The newly drafted Williams joins a crowded field that also includes Fred Jackson, Bryce Brown and Anthony Dixon. Jackson led the team with 525 rushing yards on 141 carries last season, but he is now 34 years old and there is no guarantee he can produce another above-average season.

Buffalo has a whopping 13 receivers on its depth chart right now, so obviously some of those guys will not be around when training camp begins. Sammy Watkins is a true No. 1 wideout and Robert Woods seems to have locked down the second receiver spot after his solid sophomore campaign last year (65 catches, 699 yards).

Harvin will likely get a chance to earn the majority of the snaps in three-receiver sets, but he should be pushed by the rookie Lewis, Marquise Goodwin, Marcus Easley and Chris Hogan.