Walsh is given credit for popularizing the 'West Coast offense'. The Bill Walsh offense was actually created and refined while he was an assistant coach with the Bengals. The offense utilizes a short, precise, timed passing game as a replacement/augmentation of the running game. The offense is extremely difficult to defend against as it is content to consistently make 6–8-yard gains all the way down the field. (The other West Coast offense—more focused on the vertical, or downfield, passing game—was actually created by 1960s L.A. / San Diego coach Sid Gillman, and San Diego State coach Don Coryell, who also employed a version of it as head coach of the St. Louis (football) Cardinals and San Diego Chargers during a period where it garnered the nickname "Air Coryell".)