Who has served as MLB commissioner since 2015?

Which third baseman won 16 Gold Gloves and was nicknamed "The Human Vacuum Cleaner"? Which Yankees switch-hitter won the Triple Crown in 1956? Which player won the most World Series rings as a player, with 10? Who was baseball's first commissioner, appointed after the Black Sox scandal? Which commissioner led MLB from 1992 to 2015? What is "Tommy John surgery"? Which surgeon first performed Tommy John surgery in 1974? What is the "Mendoza Line" in baseball?