A native of Lenoir, North Carolina, Walker batted left-handed, threw right-handed and was listed as 6 feet (1.8 m) tall and 170 pounds (77 kg) during his playing career.

He was signed by the Chicago Cubs' organization in 1944 and spent four full years in their farm system, where he was the All-Star catcher in the Class B Three-I League (1946) and the Double-A Southern Association (1947).

But when injury sidelined Brooklyn's Hall of Fame catcher, Roy Campanella, Walker was behind the plate in the deciding game of the 1951 National League tie-breaker series on October 3, 1951, when Bobby Thomson hit the "Shot Heard 'Round the World," costing the Dodgers the pennant.

After 1965 he was a pitching coach for the Washington Senators, New York Mets and Atlanta Braves, working closely with managers Gil Hodges, Yogi Berra and Joe Torre, among others.

He also served as the club's emergency manager from September 25–29, 1968, after Hodges suffered a mild heart attack and went on medical leave for the final four games of the season; under Walker, the Mets were 2–2.