On the WIS forums is a link to a formula created to simulate Wins Above Replacement. We at Get Up Get Up Get Outta Here Gone plugged them in, and here is what the results were:
As a bonus, at the bottom are the top 10 seasons by position players and pitchers since Season 45.
Top Twenty-Five Position Players:
Top Twenty-Five Pitchers:
Top Twenty-Five Relievers (7 starts or less)
Top Twenty-Five Offensive Seasons based on Weighted Runs Above Average:
Top Ten Defensively at Each Position:
And the dubious least valuable position players and pitchers:
Top Ten Individual Seasons Since 45: