Sanguillén was born in Colón, Panama. He was notorious for being a "bad-ball" hitter. Most pitchers will try to strike out an aggressive, free-swinging hitter by forcing him to swing at pitches outside the strike zone when he has two strikes on him. Sanguillen often irritated opposing pitchers and managers by hitting bad pitches for base hits. He rarely walked, and was the only player since 1900 with at least six straight seasons with 475 plate appearances and fewer than 22 walks. This was also why, in spite of his high batting average, his on-base percentage was lower than the league average over his career.