Plácido Enrique Polanco is a Dominican-American former professional baseball player. He played in Major League Baseball (MLB) for the St. Louis Cardinals, Philadelphia Phillies, Detroit Tigers and Miami Marlins. He was a second baseman, third baseman, and shortstop. He was twice voted to start in Major League Baseball All-Star Games: in 2007, and again in 2011. Polanco retired with the highest all-time career fielding percentage for second basemen at 99.27% and the highest all-time career fielding percentage for third basemen at 98.34% which still appear to be records.

In baseball and softball, second baseman, abbreviated 2B, is a fielding position in the infield, between second and first base. The second baseman often possesses quick hands and feet, needs the ability to get rid of the ball quickly, and must be able to make the pivot on a double play. In addition, second basemen are usually right-handed; only four left-handed throwing players have ever played second base in Major League Baseball since 1950. In the numbering system used to record defensive plays, the second baseman is assigned the number 4.