In his 17-year career, Blue played for the Oakland Athletics, San Francisco Giants, and Kansas City Royals.

Baseball historian Bill James cited Blue to be the hardest-throwing lefty, and the second hardest thrower of his era, finishing only behind Nolan Ryan.

Blue had a 24-8 record in 1971, winning both the Cy Young and MVP awards. 

That 1971 season, Blue's Athletics won the American League West title for the franchise's first postseason berth since the Philadelphia Athletics in the 1931 World Series. He was the youngest American League player in the 20th Century to win the MVP Award. He was the starting pitcher for the American League in the 1971 All-Star Game, and for the National League in the 1978 All-Star Game.

Blue won 20 games in 1973 as he led the Athletics to the World Championship that year.

Blue also made a name and career after baseball for himself in the San Francisco Bay Area by donating his time to many charitable causes, mostly promoting baseball in the inner city.