Walker debuted with the Orioles in 1957 as an 18-year-old bonus baby. In 1959 he went 11-10, won a 16-inning shutout over Chicago, and became the youngest pitcher to start or win an All-Star game. His .368 batting average in 1960 was tops among ML pitchers. With the Indians in 1963, he saved Early Wynn‘s 300th career victory. He was a manager and scout in the Yankee organization and an ML coach with the Yankees and Astros.