Berenguer signed with the Mets as an amateur free agent in 1975. He went 8–1 (3.94) for the 1987 World Champion Minnesota Twins and 8–4 (3.96) in 1988. Extremely wild as a youngster, he learned to harness his 90-plus-mph fastball, which he liked to throw inside, and added a forkball. His effectiveness was aided by his intimidating appearance and disposition.
Berenguer suffered one of MLB's oddest off-field injuries while pitching for Atlanta in 1991. On an off day, while he was home wrestling with his kids, he broke his pitching arm and ended up missing the remainder of the season, also missing out on the Braves Cinderella run to the World Series that year.