Thursday, March 21, 2013
Positional adjustments
This is a good post from Dave, that talks about the positional adjustments.
It bears repeating that the positional adjustments I use are guides, and not hard-and-fast numbers. The important part in Dave's article:
Mark Smith wrote about the evolution of the catching position two weeks ago, noting that the recent trend has catcher offensive performance spiking while caught stealing rates are steadily falling, which might suggest that teams are trading have been more wiling to trade defense for offense behind the plate in the last few years. Just from an anecdotal perspective, you could find support for that idea in the crop of starting catchers being handed jobs this year — Jesus Montero, Wilin Rosario, John Jaso, and Tyler Flowers are all bat-first catchers that have poor-to-awful defensive reputations, but they’re all penciled in as big league regulars for 2013. Of course, there are also some pretty terrific defensive catchers at the beginning of their careers as well, and there have always been bat-first catchers in Major League Baseball. Just pointing at those four doesn’t prove that teams are definitely shifting towards offense behind the plate.
In a nutshell, if teams have decided to trade defense for offense at a position, then the positional adjustments need to be altered.
It's important to remember what the positional adjustment does, and again, quoting Dave:
For those who aren’t aware, the positional adjustments are a necessary component because defensive metrics calculate a player’s performance relative to his peers at that position, but an average defensive shortstop is almost certainly a superior defender to an average defensive second baseman. Same for center fielders versus corner guys, and third baseman versus first baseman.
If for example you have a league in Canada that is filled with LHH, teams may decide to shift their talented fielders from 3B to 2B. Suddenly, 2B might be as important a fielding position as SS, and 3B might be slightly more important than 1B. And we can tell based on the fielding talent of the players we find at those positions.
The problem is that we don't know the fielding talent at those positons because every fielder is being compared to his positional peer, meaning the average at each position is... well, average. We need some independent way to put them on the same scale.
I did this based on players who play multiple positions, and seeing how their performance compares to their peers. This is no different than say park factors or league factors. If you get better numbers as you go from park A to park B, or league A to league B, or position A to position B, then that means your competition got worse in situation B compared to situation A. (Change in your own talent notwithstanding.)
Another way you can do this is look at offense at that position. If you see a sudden rise in hitting at a position, that COULD be because you traded defense for offense. But, that's not a given. If ARod enters the league, you are not trading defense for offense necessarily. If he's a stud fielder AND a stud hitter, then where else would you put him? Same for Junior, Trout, Mantle, Mays, etc. So, you have to be careful in ASSUMING that an increase in offense is because of a decrease in defense.
You could look at the Fans Scouting Report. That's a good way, as long as you can feel comfortable you can handle the inherent observer bias. After all, it might be hard to put the fielding talent of 3B and 2B on identical scales, given that they don't show their skills in the same way or the same frequency.
You can look at how players move along the spectrum, and see if players move more or less frequently from position A to position B to position C over their careers.
There's a dozen ways to look at this problem to try to find a solution.
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