Fox spent eight years as manager of the Giants' Class C St. Cloud Rox team in the Northern League, scouted from 1957 to 1963, then managed the Giants' Triple-A Tacoma affiliate in the Pacific Coast League in 1964 before coming to the Major Leagues as a San Francisco coach under Herman Franks in 1965. He returned to the PCL to pilot the Giants' Phoenix affiliate in 1969–70 until he was summoned to San Francisco on May 24, 1970 to replace Clyde King as the manager of the MLB Giants. The Giants were stalled in fifth place in the NL West at 19–23 (.452), and had just lost a 15-inning game to San Diego, 17–16, the day before. Under Fox, the 1970 Giants recovered to go 14 games over .500 and finish third, 16 games behind Cincinnati.