1B, on an offensive and defensive value sum total, is the easiest position to fill, by far. I mean, for example, the Cubs basically are stuck with 3 above average first basemen on their roster (Fox, Hoffpauir and Lee). Adam Dunn signed for a mere 8 million this off season. Its the easiest defensive position on the field, as a result, anyone can play it, so it gives you the widest range of talent to fill any void there. When compared to Shortstop, where there's 10 people who can play it defensively above average and can OPS over .750 in MLB.