Etheridge played college baseball at Mississippi State University for two seasons before signing with the San Francisco Giants as an amateur free agent in 1964.

After three seasons in the Giants' farm system, he made his major league debut on July 16, 1967 in the first game of a doubleheader against the Chicago Cubs at Candlestick Park.

[1] The next day, he made his first major league start; with the Giants down 4-1 in the ninth inning, Etheridge hit a two out triple to drive in Bob Schroder and Jim Davenport.

Though he struggled for playing time behind slugger Jim Ray Hart at third base, Etheridge was named a rookie All-Star by Topps.

After half a season with the Salt Lake City Bees, he was dealt from the Padres to the St. Louis Cardinals for Ron Willis before the trade deadline on June 15, 1970.