Let the speculation begin. Here is a rundown on top head coaching candidates who could be on the Buffalo Bills’ radar in the wake of Monday’s firing of Chan Gailey:

Jon Gruden, 49, ESPN broadcaster. Gruden won a Super Bowl with Tampa Bay and went 95-81 in 11 seasons as head coach in Tampa and Oakland. He’s the sexy hire who will be pursued by many.

Jay Gruden, 45, Cincinnati offensive coordinator. Gruden worked on his brother’s staff in Tampa for five years and spent 12 years coaching arena football. He has done a good job with Andy Dalton the past two years.

Bruce Arians, 60, Indianapolis offensive coordinator. Arians won two Super Bowl rings in Pittsburgh. He was Steelers offensive chief for five years. He did a great job as interim head coach with the Colts this year.

Mike Zimmer, 56, Cincinnati defensive coordinator. He has 13 years experience as a defensive chief, the last five with Cincinnati. Aggressive. Fiery. His Bengals have been in the top seven three of the last four years.

Ken Whisenhunt, 50, ex-Arizona head coach. Went 49-53 with the Cardinals the last six years. He took the Cards to the Super Bowl in 2008. A good offensive mind who couldn’t find a QB after Kurt Warner retired.

Mike McCoy, 40, Denver offensive coordinator. He has run Denver’s offense the past lour years. He did a great job getting the most out of Tim Tebow last season and worked with Peyton Manning this year.

Doug Marrone, 48, Syracuse head coach. Marrone worked as Jets O-line coach and was Sean Payton’s offensive coordinator in New Orleans from 2006 to 2008. He’s 25-25 in four seasons at Syracuse.

Ray Horton, 52, Arizona defensive coordinator. Won a Super Bowl as a player and two as a Steelers defensive backs coach. Tutored under defensive guru Dick LeBeau as a player and coach.

Perry Fewell, 50, New York Giants defensive coordinator. Fewell was passed over by the Bills in 2010 and won a Super Bowl ring with the Giants last year. Would he grant the Bills an interview after getting snubbed last time?

Russ Grimm, 53, ex-Arizona offensive line coach. A Hall-of-Fame guard, Grimm has coached offensive line the last 16 seasons. He’s an executive presence who would get players to play hard. The Bills had some interest last time.

Dirk Koetter, 53, Atlanta offensive coordinator. He’s near the top of the “hot assistant” list and reportedly is on the radar of the Eagles, Chiefs and Browns. A former head coach at Boise State (26-10) and Arizona State (40-34).

Chris Petersen, 48, Boise State head coach. An innovative offensive mind, Petersen is 84-8 at Boise. Might not want to leave. He signed a deal in February that pays him $2.2 million in 2013.

Kyle Shanahan, 33, Washington offensive coordinator. He’s the son of Washington’s head coach who seems destined to get a head job some day. Already has coached nine NFL seasons, with a lot of good people.

Greg Roman, 40, San Francisco offensive coordinator. Smart play-caller for Niners coach Jim Harbaugh. He has 15 years experience in the NFL. He was the roommate of Atlanta personnel chief David Caldwell at John Carroll.