Nearly every NFL offseason includes at least one unexpected head coach departure, and on Thursday afternoon, the Buffalo Bills' Mike Mularkey provided the surprise factor for this year's cycle of firings and hirings. In a lengthy meeting with Bills management, Mularkey stunned owner Ralph Wilson and newly appointed general manager Marv Levy by tendering his resignation after only two seasons on the job, ESPN.com confirmed. His departure will be confirmed by the Bills at a Friday news conference scheduled for 11 a.m. ET. Team officials declined comment on Thursday evening. Sources close to Mularkey said Thursday night that he has already left Buffalo. Wilson and Levy were said to have been taken aback when Mularkey contacted them Wednesday and acknowledged he was mulling his resignation.