Position Adjustments

Back before the winter meetings started and there were all kinds of trades and free agent signings to analyze that took up all of our writing here, we were all ridiculously excited about the addition of UZR data the FanGraphs statistics section. Now that we have a lull in transaction analysis, I want to get back to talking about UZR, fielding metrics, and evaluating the best ways to view them. Most of my posts the rest of the week will focus on these issues.

Starting off, I want to talk about positional context. If I asked you who the best defensive player in baseball was, would your answer be Carl Crawford? Probably not. He’s definitely an asset defensively, but does anyone think he’s really the best defensive player in the game? His 2008 UZR/150 is better than everyone else, though, so if you were just sorting the entire league by that metric, Crawford stands head and shoulders above everyone else.

However, we all instinctively understand that the quality of defenders at each position is not even. Crawford rates remarkably well as a left fielder in large part due to the fact that left fielders are lousy defenders as a group. In fact, if we just look at UZR/150 for qualified left fielders in 2008, only three of the 13 players on the list have above average rankings – Crawford at 28.6, Fred Lewis at 12.1, and Matt Holliday at 5.2. The bottom of the list is populated by guys who should be DH’ing – Pat Burrell, Raul Ibanez, and Adam Dunn. Teams use left field as a hiding ground for good hitters with lousy defensive abilities in order to get their bats in the line-up, so when a team like Tampa goes the alternate direction and sticks a good glove in LF, he’s going to look like a superstar, thanks to the relative uselessness of his peers.

If Crawford played CF, which is his more natural position given his defensive abilities, he’d certainly rate a lot lower than +28 runs. This isn’t because CF is any harder to play than LF, but simply because the people he would be compared to are much better defensively than the people he’s compared to as a left fielder. This should seem somewhat obvious, but I’ve seen a lot of people talk about relative defensive rankings for up the middle players being lower because of the harder nature of the position, but it’s really just the peer group that is chosen for comparison.

If Carl Crawford was put into a room of 5’5 people, he’d appear tall. If he was put into a room of 6’5 people, he’d appear short. Think of left field, right field, first base, and designated hitter as positions of short people. You don’t have to actually be the best defensive player in the league to look like a defensive whiz when the standard you’re being held to is so low.

This is why, when you see us talking about total value of a player, you’ll see position adjustments come up in the discussion. Since each player is being rated by UZR relative to average at that position, we have to come up with a scale that neutralizes all of the averages so that they’re somewhat similar to each other.

Tom Tango has developed the most commonly accepted set of positional adjustments out there right now, based on historical data of how players perform when they move from one position to another. His scale is as follows:

Catcher: +12.5 runs
Shortstop: +7.5 runs
Second Base: +2.5 runs
Third Base: +2.5 runs
Center Field: +2.5 runs
Left Field: -7.5 runs
Right Field: -7.5 runs
First Base: -12.5 runs
Designated Hitter: -17.5 runs

Essentially, the width of the spectrum of major league players being used at their best positions is about 30 runs – if you have a league average defensive catcher and you make him a full time DH, you’ve whacked about three wins off of his value.

These positional adjustments match up with common knowledge pretty well – catchers are scarce, shortstops are the best non-catcher defenders, and the immobile stiffs get hidden at DH/1B/LF/RF, depending on how just how immobile they really are. It’s the middle part of the spectrum – second base, third base, and center field – that cause some disagreement. We’ll get into those three positions specifically this afternoon.




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Dave is a co-founder of USSMariner.com and contributes to the Wall Street Journal.


14 Responses to “Position Adjustments”

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  1. d says:

    why wouldn’t it be 5 runs from catcher to DH (vs. 3), not sure I follow that reasoning.

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  2. Dave Cameron says:

    Catchers are +12.5, DHs are -17.5. The absolute value difference between those is 30 runs, which translates to three wins.

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  3. One thing I notice (which may or may not have any significance), is that the position adjustments for all positions excluding DH sums to 0. This seems to make sense–the position adjustments are “normalized” in some sense, so that you’re not under- or overvaluing players in general.

    Once you include DH, however, that falls apart. Does this mean that after applying positional adjustments, we have a net undervaluing of all players? Should positional adjustments be normalized differently in the AL and NL to prevent this?

    Thanks in advance for any responses.

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    • One problem with normalizing AL and NL position adjustments differently is that it would become more difficult to compare players across leagues, so that doesn’t seem like a good solution.

      Relatedly, if position adjustments were renormalized to prevent undervaluing, we have to keep in mind that there are fewer DHs than players at other positions. So to prevent overvaluing, we wouldn’t want the position adjustments to sum directly to zero, instead, the weighted (by the number of positional slots) position adjustments would sum to zero.

      All of this assumes that this is even relevant / a problem.

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  4. Sky says:

    Dave, I obviously love that you’re talking about this. And you do a great job of explaining it well.

    One thing that might deserve clarification — why do teams stick Burrell/Dunn/etc in LF instead of CF? There IS some inherent difficulty difference between LF and CF, which is why the better defenders get stuck in CF. Or, if you don’t like to talk in terms of difficulty, you could say that CFs have more opportunities to show off their skills — more balls are hit their way.

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    • Dave Cameron says:

      Right, I’d phrase it in the latter way – teams hide players at positions where they’ll have the least amount of opportunities to display their awfulness. They play LF instead of CF because LFs get fewer chances to screw up.

      I wouldn’t say CF is harder to play than LF, only that the extra opportunities magnify defensive abilities, both good and bad. And for lousy defenders, magnification of that lousiness is not what teams are looking for.

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    • Margery says:

      There is a critical shortage of ionfrmatvie articles like this.

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  5. lookatthosetwins says:

    One thing I’d like to know is, how much value does Crawford gain by being in center field? I would guess not as much as most people think. The position adjustment and the increased competition should cancel out so the only thing adding value is the amount of balls he gets. So I guess I’m wondering what the increase would be in balls in his zone, and how much value does that actually increase? How much value does Manny lose if he gets moved to center?

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    • Sky says:

      Assuming league-average talent at a position (well, maybe right in-between the average of the two positions being considered) and a league-normal skillset, there shouldn’t be much benefit or cost to moving a player, beyond the learning curve.

      But as players get much better than positional-average, moving them to a tougher position allows them to show off more of their skills, because they receive more opportunities. And moving crappy fielders to “easier” positions is a good move, because their gap below average will shrink. It’s an absolute change versus percentage change thing. The further you are away from zero, the more a percentage change will matter.

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  6. philosofool says:

    Dave,

    Shouldn’t SS defense be more valuable that 1B defense in part because of the number of balls that the player is eligible to field?

    I would think that this is the primary reason that CF is considered a defensive “premium” position while the others are not. (Since a CF will see twice as many play opportunities each 1% difference in the rate at which he makes plays counts twice as much in a sense.)

    How does the rate at which balls enter the region where a field could get them affect defesive adjustments and the value of defesive abilities?

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  7. Lark11 says:

    Dave,

    How do you arrive at the -17.5 runs for the DH? I’m a little unclear on how you establish the positional adjustment for a player that doesn’t play defense.

    Thanks!!

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    • Dave Cameron says:

      We start by figuring out where DH’s come from. In pretty much every case, a full time DH is a miserable defensive LF or 1B. The guys who end up as designated hitters are guys who couldn’t hack it in the field. Therefore, we know that the DH population has to be a subset of bad defensive first baseman, and therefore, will be worse defensively as a group than first baseman. Therefore, they have to be worse than -12.5.

      So, if we look at the performance of DH’s when they play 1B, they’re usually something like 10 runs worse than average as a group. That would make the positional adjustment -22.5. However, we bump it back up to -17.5 to account for the fact that it’s harder to hit while DH’ing than it is while playing the field – the evidence for this is in The Book by Tango/Lichtman/Dolphin.

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  8. d says:

    I should read better… I saw runs and then 3 wins, my mind substituted… thanks for clarifying

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