After playing for three years in the minor leagues, Sanguillen joined the Pirates in 1967, playing in 30 games. He played another season in the minor leagues in 1968, before returning to the Major Leagues in 1969. He replaced Jerry May as the Pirates starting catcher and posted a .303 batting average. He solidified his reputation as one of the top hitting catchers in baseball by hitting for a .325 batting average in 1970, finishing third in the National League batting championship behind Rico Carty and Joe Torre.