Arthur Mahaffey Jr. (born June 4, 1938) is an American former professional baseball starting pitcher, who played in Major League Baseball (MLB) for the Philadelphia Phillies (–) and St. Louis Cardinals (). He batted and threw right-handed. In a seven-season MLB career, Mahaffey posted a 59–64 record, with 639 strikeouts, and a 4.17 earned run average (ERA), in 999.0 innings pitched. Mahaffey was signed as an amateur free agent by the Philadelphia Phillies on June 29, 1956, out of Western Hills High School (Cincinnati, Ohio). He began his Minor League Baseball career that summer. After 4 seasons playing in the Phillies' farm system, he received his MLB call-up, playing in his first Phillies game on July 30, 1960; Mahaffey pitched the final two innings of a game against the St. Louis Cardinals. He retired the three batters he faced in the eighth inning. In the ninth, Bill White led off with a single to right field and then was picked off by Mahaffey at first base. The next batter, Curt Flood, singled to center field, and he, too, was picked off by Mahaffey, who threw to first with Flood tagged out on a throw from first to second. He finished the season with a 7–3 record, an ERA of 2.31, 14 games played, while finishing third in the 1960 National League (NL) Rookie of the Year balloting (which was won by Frank Howard of the Los Angeles Dodgers). Mahaffey set a club record with 17 strikeouts in a game against the Chicago Cubs on April 23, 1961. Though he ended the season with an ERA of 4.10, and a record of 11–19 (leading the NL in losses), in 36 games, he was selected to represent the Phillies on the NL All-Star team. Mahaffey ended the season with a record of 19–14, and a 3.94 ERA, with a career high 177 strikeouts, in 41 games. He was selected again in 1962 for the NL All-Star team, finishing 26th in balloting for NL Most Valuable Player (MVP), despite leading the league in home runs allowed with 36, and earned runs allowed with 120. Mahaffey had a 7–10 record in 26 games with the Phillies, to go along with a 3.99 ERA. In , he finished the season with a record of 12–9, with an ERA of 4.52, in 34 games. The ill-fated 1964 team was in first place in the NL, with