I know this has been logged, but I'd figure I'd chime in and perhaps offer some helpful info. I am experiencing this problem as well. All across my league the AI is playing pitchers with low endurance ratings as starters (3-4 on a 10 scale). These pitchers are not gassing out after 40 or 50 pitches; in fact they seem to be as capable of throwing 100 or more pitches as high-endurance pitchers before becoming fatigued. This is really jarring because it basically means the endurance rating is meaningless, and there's nothing to distinguish a starter from a reliever. Coaches/scouts off, pitcher endurance setting at low, league modifiers at default.
Here a few examples (none of these guys are on my team):
ImageShack - Hosting :: pitcher1cn3.jpg
ImageShack - Hosting :: pitcher2jb1.jpg
ImageShack - Hosting :: pitcher3iz8.jpg.