López returned to the postseason with Houston in 1986, but he was the losing pitcher in Game Five of that year's National League Championship Series.

After his retirement from baseball, López served as municipal president of his hometown of Tecamachalco, Puebla, Mexico from 1989 until his death.

[1] López caught the attention of scout Ramon "La Chita" García of the Mexico City Reds in the Mexican League.

The Royals also purchased the contracts of Mexican League players Orlando Cepeda and 16-year-old Germán Barranca in the same month.

[5] During the 1977 Mexican League season, López earned a 19–3 win–loss record, a 2.01 ERA and 165 strikeouts over 157 innings in 73 games.

He joined the Springfield Redbirds of the Class AAA American Association for 1978, but returned to the major leagues during the 1978 season, earning a 4–2 record with the St. Louis Cardinals.

[7] After one season in St. Louis, López was traded to the Detroit Tigers with Jerry Morales for Jack Murphy and Bob Sykes.

[9] López suffered from shoulder problems during spring training in 1982, and he was demoted to Detroit's Class AAA minor-league affiliate in Evansville by July.

[9] He was called back up to Detroit on September 1, but later that month he shocked his teammates by announcing that he was giving up his MLB career and returning to Mexico.

López said that his reasons were personal, and he cited his family, the education of his children and the Mexican economy as motivating factors for the decision.

[13] 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.

[14] 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.

"[15] While in Detroit, López had earned the nickname "Señor Smoke", as he hailed from Mexico and threw a powerful fastball.

[24] López's career save total was the highest among Mexican pitchers in MLB until Joakim Soria surpassed the mark in 2010.

Facing great opposition from the previous ruling family and even enduring shots fired at his home, he described his post as "like coming into a game with the bases loaded.

"[26] Detroit rock band Electric Six named their album Señor Smoke (2005) in López's honor.

[31] In 2020, López was selected as the relief pitcher on the Mexican League Historic Ideal Team by a committee of baseball journalists and historians.