According to the
OOTP 11 manual:
Each player in OOTP has a certain amount of 'rust' after an offseason. For each at-bat or inning pitched during Spring Training, a player shakes off some of that rust. Therefore, it is important to make sure all your key players get at least some playing time during Spring Training, because rusty players won't perform well.
and
Players learn positions much more quickly when they play them during Spring Training. See Learning New Positions for more information about new positions. Additionally, players are slightly more susceptible to injuries during Spring Training.
The way we do Spring Training (all in one sim) forces teams to play their opening day lineup to ensure that regular starters shake off their rust. I would prefer a 2-week sim where I can play my younger guys on the 40-man, and a 2nd 2-week sim where I can plug the starters in. As it is now, I have to choose between giving the future stars a shot all month and risk my regular players starting the season with "rust" (whatever that factor is...only the devs know what it affects), or playing the regulars to get rid of the rust. The only tool I have that's any different from the regular season is to start the backups/young guys every 2nd/3rd/4th/etc. game, but that's not an option for the pitching staff and still doesn't allow you to get the REALLY raw guys on the field with 8-10 extra position players hanging around.
