On January 12, 2015, the Buffalo Bills named Rex Ryan the 18th head coach in franchise history. Ryan enters his first season as Buffalo's head coach and his 19th season in the NFL coaching ranks.

Ryan joins the Bills after spending six seasons as the head coach of the New York Jets. Ryan ranked third in Jets history with 50 wins (regular season and post­season) during his tenure in New York. His 4-2 record in the postseason was the best in franchise history. Ryan led the Jets to the postseason in his first two seasons with the franchise in 2009 and 2010 as the team advanced to the AFC Championship game in both postseason appear­ances.

Ryan's 46 regular season wins during his time with New York rank as the third most in Jets history behind Weeb Ewbank (71) and Joe Walton (53).

Renowned for his defensive prowess, Ryan inherits a Bills defense that finished 2014 allowing the fewest points per defensive drive (1.41) in the NFL and also led the league in sacks with 54 quarterback take­downs.

From 2009-2014, the Jets ranked first in the NFL in passing yards allowed (204.3), opponent completion percentage (55.7), opponent first downs (1,667), and yards allowed per defensive play (4.9). The Jets ranked second in total yards allowed per game (306.9).

The Jets defense saw an immediate improvement upon Ryan's arrival in New York, improving from the 16th ranked defense in 2008 to the league's top defense in 2009 allowing just 252.3 yards per game in Ryan's inaugural season as the Jets head coach.

Ryan's Jets defenses would go on to rank in the top 10 of the NFL in five out of his six years as head coach (2009-1st, 2010- 3rd, 2011-5th, 2012-8th, 2014-6th).

Ryan's 2013 version of the Jets defense didn't land among the top 10 NFL de­fense, but still ranked well in several other categories including third in the NFL in rushing defense (1,412 yards allowed) while finishing first in opponents' per carry average (3.4). The defense also produced 41 sacks, the most by a Ryan led defense since his 2006 Ravens had 60 and the most by a Jets defense since it also produced 41 in 2008. Pacing the team were career-best performances from defensive lineman Muhammad Wilkerson (10.5) and linebacker Calvin Pace (10.0), who became the first pair of Jets de­fenders to both produce double-digit sacks since Joe Klecko (20.5) and Mark Gastineau (20) accomplished the feat in 1981.