Another likely outcome is the arrival of prospects to the majors who also derive their value from playing those positions. While organizations like to think they have a pretty accurate timeline when good minor leaguers will hit the majors, it is far from being completely accurate and unexpected and faster arrivals occur. If a shortstop was ready to be promoted on a team with a mid-tier shortstop, it would be almost impossible to get value from both of these players. However, for corner outfielders and infielders it is much easier to move players around and get value out of everyone.

Remember that the expected value is a weighted average of all probabilities of expected returns. Defensive decline and prospect congestion are both outcomes that hurt non-elite middle infielders more than corner outfielders and infielders, and their value is subsequently hurt. Those who are paid ‘elite’ salaries are those who would still be valuable if moved away from their position, meaning that the aforementioned outcomes are not nearly as hurtful to their value.

Finally, the correlation of .21 just shows me that 21% of wins are explained by the middle infielders, which is more than their share of at bats and defensive contribution. This would be evidence that they are more important than their individual contributions, but you also have to consider some dependence as teams with great shortstops have frequently addressed a lot of other needs first. The starting middle infielders probably make up about 20% of offensive opportunities and I’ll assume a 10% contribution to runs prevented. This would cause one to expect a 15% r^2 value (.5 * .2 + .5 * .1 ) if the variables were independent. Since this is not the case, one could say that the wins added are pretty proportional to what you would expect from 2 starting position players.