Unless you have five starters better than him, it's not really a redundant position. Not redundant, but limiting returns. I don't quite get that. The return is in the runs over his replacement, not in the overall team offense or defense. Until you start getting into the extremes of the marginal values of runs in high- or low-scoring environments, that is. If you have the best pitching in the league with Shawn Estes as your fifth starter, and a mediocre offense of eight guys just below average, you are still getting more value by replacing Estes than improving the batting.