it can mean that, but doesn't have to. Those three pitcher spots allow you to customize your team's staff to the best pitchers on your team or the catagories you are chasing.
If for example you had four great starters and a really bad one, you might find it easier to plug in a good reliever who helps you in ERA and WHIP, while getting you some saves. You lose out on a few wins, but that's the tradeoff. In general, plug in your best pitchers. Towards the middle/end of the season, you may want to look at the standings and adjust accordingly. For instance, if the next three guys above you only have 5 or 10 more saves then you, but wins are very spread out, maybe you'd want to toss in more relievers to try and catch up on saves.