[Getch]

From the manual, and post http://www.ootpdevelopments.com/boar...d.php?t=146453:

13.9.4. Learning New Positions
Players learn new positions through practice. The best way to accomplish this is by having them play in a new position. Players learn more quickly when they play regularly in the minor leagues, or in spring training. The more a player plays at a certain position, the more he improves. After he has acquired a certain amount of experience at a position, he will be given a position rating that will display on his profile.

The defensive spectrum is as follows: DH - 1B - LF - RF - 3B - CF - 2B - SS. Generally speaking, the further to the right, the harder the position is to play and the harder it will be to convert a player to that position. Position players can learn to play catcher, but it often takes a very long time, and they typically don’t make very good ones.

Note: A player cannot “lose” positions. Once he has learned a position, he will always have a rating at that position.