Forster was a phenom at 18, a glutton at 34. In between he notched 127 saves. Signed out of high school, he pitched just 10 games in A-ball in 1970, and was so impressive he made the White Sox the following April. In 1972 he broke a club record with 29 saves. In that last year before the DH rule, he batted .526; he was a .397 lifetime hitter. From 1971 to 1973 he hurled 138-1/3 innings without surrendering a home run. He was the AL Fireman of the Year in 1974, saving a league-high 24 games. His fastball was clocked at 94.9 mph that September 7, but by the next season he was on the shelf with a bad arm; most felt he had been overworked by manager Chuck Tanner. After going 2-12 in 1976, mostly as a starter, he was traded to Pittsburgh with Rich Gossage (whom Chicago had also made a starter) for Richie Zisk and Silvio Martinez.
In November of 1977, Forster became the first free agent ever signed by the Dodgers. He rebounded with 22 saves and a 1.94 ERA for the 1978 pennant winners, but had bone chips removed from his elbow after the World Series. He was sometimes effective from 1982 through 1986, constantly battling weight problems. His eating habits began attracting national attention. He was with the Braves when, in June 1985, Late Night host David Letterman made Forster a national celebrity by calling him “a fat tub of goo.”