 Complete the following phrase:  The single-wing continued to be in wide use throughout this, and a number of forward-passing tailbacks became stars, including Sammy Baugh of the Washington Redskins. In 1939, University of Chicago head football coach Clark Shaughnessy made modifications to the T-formation, a formation that put the quarterback behind the center and had him receive the snap directly. Shaughnessy altered the formation by having the linemen be spaced further apart, and he began having players go in motion behind the line of scrimmage before the snap to confuse defenses. These changes were picked up by Chicago Bears coach George Halas, a close friend of Shaughnessy, and they quickly caught on in the professional ranks. Utilizing the T-formation and led by quarterback Sid Luckman, the Bears reached the 