- Mario Guerrero played in the majors from 1973-1980. Mario was signed by the New York Yankees in 1968. He played in their farm system from 1968-1972 before being traded (with Danny Cater) to the Boston Red Sox for Sparky Lyle. Guerrero finished the 1972 season in AAA Louisville.
- Guerrero made the Boston ballcllub in 1973 and batted .233 in 63 games as Luis Aparicio's backup. In 1974 Mario began the season as the regular shortstop but was eventually replaced by Rick Burleson. Guerrero batted .246 in 93 games in 1974. At the end of spring training in 1975 Mario was traded to the St. Louis Cardinals for a player to be named later (Jim Willoughby was sent to the Red Sox on July 4 to complete the deal).
- Guerrero started the 1975 season in AAA Tulsa and was brought up to the Cardinals in mid-May. He batted .239 in 64 games for the Cardinals in 1975. Mario started the 1976 season back in Tulsa and was traded to the California Angels on May 29 for two minor leaguers. Guerrero batted .284 in 83 games for the Angels in 1976. In 1977 Mario split time with Rance Mulliniks at shortstop and batted .283 in 86 games.
- After the 1977 season Guerrero became a free agent and signed with the San Francisco Giants. Before the 1978 season Mario was included in the big trade with the Oakland A's that sent Vida Blue to the Giants. Mario became the A's starting shortstop and batted .275 in 143 games. Mario backed up Rob Picciolo in 1979 and batted .229 in 46 games. Guerrero regained his starting job in 1980 and batted .239 in 116 games.
- After the 1980 season Guerrero was sold to the Seattle Mariners. He didn't make the Mariners ballclub in 1981 and was released at the end of spring training.
- Guerrero worked as a buscon (guys who hunt for baseball prospects in the Dominican Republic) after his playing career. Guerrero sued Raul Mondesi for one percent of his baseball earnings in 1998 and eventually won $640,000 (plus $422,000 interest) in 2004. The judgement was thrown out on appeal in 2005. He previously won a similar case against Geronimo Berroa.
2017 Allen & Ginter: Box 4: Packs 9 - 16
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