In many cases, a manager is a former professional, semi-professional or college player. From 1901 to 1981, 21% of MLB managers had played catcher during their playing career--the most common. Outfielders made up 16.6% and second basemen made up 13% of managers. Over the same period, managers who were second basemen had the highest winning percentage. The manager's responsibilities normally are limited to in-game decisions, with off-field roster management and personnel decisions falling to the team's
general manager. The term
manager used without qualification almost always refers to the field manager (essentially equivalent to the head coach in other North American professional sports leagues), while the general manager is often called the GM. This usage dates back to the early days of professional baseball when it was common practice for teams to have just one "manager" on their staff, and where GM duties were performed either by the field manager or (more commonly) by the owner of the team. Some owners (most famously,
Connie Mack of the
Philadelphia Athletics) carried out both GM and field managerial duties themselves. Major League Baseball managers differ from the head coaches of most other professional sports in that they dress in the same uniform as the players and are assigned a jersey number. The wearing of a matching uniform is frequently practiced at other levels of play, as well. The manager may be called "
skipper" or "skip" informally by his players. ==Baseball Hall of Fame managers==