Sanguillen was a valuable member of the world champion 1971 Pirates. He had his best year in terms of offensive production by hitting for a .319 batting average, while hitting 7 home runs and 81 runs batted in. He also had his best year defensively, finishing third among National League catchers in games caught (135), second in base runners caught stealing (37), caught stealing percentage (51.4%), fielding percentage (.994) and first in assists (72). The Pirates won the National League Eastern Division pennant by 7 games over the St. Louis Cardinals, then defeated the San Francisco Giants in the 1971 National League Championship Series, before winning the World Series against the Baltimore Orioles. In the seven-game series, Sanguillen had a .379 batting average with 11 hits, second only to the 12 hits by Roberto Clemente.