Without knowing the ins-and-outs of the Diamond Mind runs saving accounting systems, I can't speak to the strengths and weaknesses of it. I do know the Plus/Minus system and Stats Inc's methods so I can rely on that. I will say this, Plus/Minus does not think outfield arms costs nearly as many runs Diamond Mind seems to think - even from the worst CF arms - and I tend to agree with that, even factoring in the distances of the throws. What's more is that Span's arm hasn't been substantially better than Revere's to even merit the consideration of pushing him out of center field a given. P/M finds that Revere's arm - although rated one of the worst - was only 3 runs below average. Span, whose arm was also fairly bad last year, was 2 runs below average - making him at the bottom of the list - and he was run on at about the same frequency as Revere. In his introduction to center field and Target Field in 2010, Span struggled with (1) the leadership role of center, failing to call off corner outfielders and pulling up to allow a Cuddyer or Kubel to attempt to get a gapper when he had the ability to get to it and (2) the wind effects of Target Field. Now, Span did improve in both areas in 2011 but Revere, in his first year, was much more poised at the position and carried a bit of that Carlos Gomez catch-it-at-all-costs attitude when patrolling center. As I said before, there's a 100 additional plays in CF each year versus the corners so I would prefer to have the better fly-catcher out there and, so far, I believe that is Revere. I've seen this scenario outlined before and I can't recall if Span cheating towards right this was mentioned by Gardy in the winter caravan or not. Here's the thing, I don't believe this will play out in reality. While you would want to have that alignment, the majority of hitters in baseball are right-handed and thus Span will likely cheat towards left. Of course, I'm sure the outfielders will be positioned on a case-by-case basis depending who's hitting, pitching, and what the runner and outs situations are. In the end, I don't think it is a bad decision to go Revere-Span-Willingham in the outfield. That's still a very above-average defensive alignment 2/3rds of the way through.