Walker pitched in parts of four seasons for Baltimore from 1957 to 1960 during the first half of his eight-year MLB career. He enjoyed a breakout season with the Orioles in 1959, when he became the youngest pitcher in MLB history to start the All-Star Game at 20 years, 172 days old, and was the first Orioles pitcher to earn the opportunity.

The Ada, Oklahoma, native went on to post a 2.92 ERA that season, a figure that ranked among the top five in the American League. He pitched out of the bullpen and rotation, finishing the year with an 11-10 record, seven complete games, four saves and 100 strikeouts in 182 innings. His most notable performance was a 16-inning shutout of the Chicago White Sox, a feat that has been matched only twice since.

Walker followed that up with a solid 1960 season before the Orioles traded him and outfielder Chuck Essegian to the Kansas City Athletics in April 1961 for pitcher Dick Hall, a member of the Orioles Hall of Fame who won two World Series in Baltimore, and outfielder Dick Williams, who went on to be enshrined in Cooperstown as a manager.

After his playing career, Walker was a pitching coach for the New York Yankees and Houston Astros. He also managed in the minor leagues and worked as a scout before rising to general manager of the Detroit Tigers. Walker then worked in the front offices of the St. Louis Cardinals and Cincinnati Reds before retiring in 2019.

The announcement of his death comes one day after the 2024 All-Star Game in which pitcher Corbin Burnes represented the Orioles as the AL starter and Pittsburgh Pirates rookie Paul Skenes, 22, became the sixth-youngest pitcher to start the Midsummer Classic as the opening pitcher for the National League.