In 1968, Walsh moved to the AFL expansion Cincinnati Bengals, joining the staff of legendary coach Paul Brown. It was there that Walsh developed the philosophy now known as the "West Coast Offense", as a matter of necessity. Cincinnati's new quarterback, Virgil Carter, was known for his great mobility and accuracy but lacked a strong arm necessary to throw deep passes. Thus, Walsh modified the vertical passing scheme he had learned during his time with the Raiders, designing a horizontal passing system that relied on quick, short throws, often spreading the ball across the entire width of the field. The new offense was much better suited to Carter's physical abilities; he led the league in pass completion percentage in 1971.