Although born in Argentina, Guillermo Naylor came from a British background, and was part of the ex-pat community that helped popularize polo in the South American country in the early part of the 20th century. Naylor founded the Sundowners Polo Club in 1919, which was one of the founder members of the Argentine Polo Association in 1922.
A 7-handicap player, Naylor was a member of the Santa Inés team that won the Argentine Open in 1922, 1924, and 1928. He was called up for the 1924 Olympics but played only in the final round-robin match, which Argentina won 15-2 against France with the gold medal already secure. His other major titles included winning the Hurlingham Open in 1931, and winning at the Cámara de Diputados, Interestancias, Joseph Drysdale, and Hurlingham Ladies’ Nomination Cups.