As a rookie reliever for the Giants in 1973, Sosa went 10-4 with 18 saves (tied for fifth in the NL) in 71 appearances (third in the NL). He dropped to 9-6, seven saves in 1974, when Randy Moffitt took over as the Giants’ stopper, and Sosa was traded after the season. He pitched poorly for three teams in the next two years before rebounding with the NL champion Dodgers in 1977, going 2-2 with a 1.97 ERA. He lost the LCS opener and was also hit hard in the World Series. Waived to the Pirates in January 1978, he was then traded to the A’s on April 4 and went 8-2 with 14 saves.
The Expos picked up Sosa for 1979, and he rewarded them with an 8-7, 1.95, 18-save season. He went 9-6, 3.06 with nine saves in 1980, and declined thereafter.