Currently there are no multi-game injuries that you have to worry about, although players will get tired (see fatigue below). What that means is that you may have someone unable to finish a game due to being hit by a pitch for example, at which time the SimManager will bring someone in off the bench. Injuries not withstanding, subs also come into play primarily in pinch-hitting situations and if you plan on platooning 1 or more players at various positions, e.g. your strategy might be to take a decent right-handed 3rd baseman and a decent left-handed 3rd baseman instead of taking a great right-handed 3rd baseman.