A relief pitcher who didn’t rely on gimmicks, the well-traveled McMahon threw a fastball and a simple overhand curve for 18 ML seasons, and when he retired, only Hoyt Wilhelm, Lindy McDaniel, and Cy Young had pitched in more games. McMahon played before the dominating bullpen closer had emerged as a baseball position, and he never saved more than 19 games in a single season, but the stocky righthander was always in demand as a durable, hard-throwing reliever.
McMahon was converted to relief pitching in the minors by manager Whitlow Wyatt after he had gone 2-13, 5.01 as a starter for Toledo (American Association) in 1955, and in 1957 he reached the ML, posting a 1.54 ERA in 32 appearances for the World Champion Braves. He led the NL with 15 saves in 1959, then in 1962 he began a sojourn that took him to seven different clubs in eight seasons. The Braves sold him to the Astros in 1962 (where he made his only two ML starts, both losses), who sold him to the Indians after 1963. McMahon saved 27 games in two seasons with the Indians, then switched teams in mid-season each year from 1966 to 1969, yet still posted a 1.98 ERA in 1967 and again in 1968. The Indians traded McMahon to the Red Sox with Lee Stange for Dick Radatz in 1966, and the Red Sox shipped him to the White Sox for Jerry Adair in 1967. Chicago traded him to Detroit for Dennis Ribant the following year, and in 1969 the Tigers sold him to San Francisco, where he spent his final six seasons. In 1971 McMahon led the NL with nine relief wins and recorded a career-high 19 saves for the Giants.