Mayo failed to hit in major league trials during the 1930s, but later benefited from the WWII player shortage. Returning in 1943 with the Athletics, he led AL third basemen in fielding average. He had never played a ML game at second base until he joined the 1944 Tigers, but he led the position in double plays that year and in fielding the next. Detroit won the 1945 World Series with 35-year-olds at shortstop and second base – Skeeter Webb and Mayo. Mayo hit .285 that year, and he remained with the Tigers well after the younger players returned from the war.