There's a load of strategy involved too.

Starting pitchers can't throw forever. You need to make the call on when to pull them from the game and use your replacements. Replacement pitchers put quite a bit of stress on their arms. They pitch for up to 3 or 4 days in-a-row, so you can't always go to the same guys.

So, when do you pull the starter? If so, who's going to hit for him in the lineup? When you use a player once in a game, there is no coming back when removed from the line up.

Do you worry about offensive production or defense? There are some outfielders that just stink defensively that become a late inning liability in close games. (Soriano) There are outfielders that are game breakers offensively and you just can't ignore their plate presence and the effects they have on the opposing team (Soriano)

Offensive strategies include "bat protection". (who is hitting behind the star player. ) Barry Bonds was a prolific homerun hitter. Nobody would want to pitch to him, so they'd walk him intentionally and send him to first base. First base isn't as costly as a home run, ya know?

So who is hitting behind Bonds? Will this hitter make the opposing team pay for the intentional walk?