Though Righetti pitched well in spring training in 1981, the Yankees did not have room for him on their roster, so he began the season with Columbus. After he pitched to a 5–0 record and 1.00 ERA with 50 strikeouts in 45 innings, the Yankees recalled Righetti from Columbus in May 1981. He was assigned uniform number 19. The Yankees reserved numbers ending in 9 for pitchers they viewed as having promise: Dick Tidrow wore 19 for the Yankees, while Catfish Hunter wore 29, Ron Davis wore 39, and Guidry wore 49. Righetti pitched strongly as a starter for the Yankees, posting an 8–4 win-loss record in 15 games started, with a 2.06 earned run average (ERA) and 89 strikeouts in 105 innings pitched during the 1981 season. Righetti won the American League's Rookie of the Year award, beating Rich Gedman and Bob Ojeda. Righetti defeated the Milwaukee Brewers twice during the 1981 American League Division Series. The Yankees reached the World Series that year; however, he was knocked out of game three of the 1981 World Series early, which was won by the Los Angeles Dodgers.