López is perhaps best known for his role as the setup reliever for the Tigers during their 1984 championship season, when he finished with a 10–1 record, 14 saves, and a 2.94 ERA. López had a 1–0 record in both the 1984 American League Championship Series (ALCS) and 1984 World Series, and he did not give up an earned run in over six innings pitched that postseason. He faced seven batters in Game Five of the 1984 World Series, retiring them all in Detroit’s 8-4 Championship-clinching victory. After the pitcher got out of two extra-inning jams to earn the win in Game 2 of the ALCS in Kansas City, Detroit manager Sparky Anderson said, "Nothing surprises me about Lopez. I've had him for five years and believe me, there's nothing like him. He's got heart and there is none better. He's one of the all-time hearts." While in Detroit, López had earned the nickname "Señor Smoke", as he hailed from Mexico and threw a powerful fastball.