Who’s the Most Underrated Player in Baseball?

Answer: Denard Span.

By one definition, at least.

If FanGraphs has one overriding purpose, it’s not, as some readers might think, to render everyone dateless. Rather, it’s to constantly ask — and attempt to answer — questions about baseball. And one of the most basic questions we ask is, “How much is [insert player’s name] worth?”

The answers are often surprising. Like, for example, two years ago, when Wins Above Replacement suggested that Ben Zobrist was the second-most valuable position player in baseball. Or how, by that same metric, we learn who’s been the real MVP in Philadelphia for the better part of the last decade.

People who read FanGraphs with some frequency have likely become accustomed to — and, hopefully, appreciate — the discrepancies between our valuation methods and more traditional ones. And those who read the site have also probably become familiar with the ways in which things like defense, positional adjustments and (now!) baserunning can affect a player’s value in sometimes dramatic ways.

Accordingly, readers probably have a sense of which players, specifically, are under- and overrated. Ben Zobrist? Generally underrated. Ryan Howard? If not overrated, per se, it’s certainly the case that he’s not flying under the radar.

There are a lot of connotations to these terms under– and overrated. The market in which a player plays and the salary he makes are certainly factors. The largest part of it, though, generally has to do with how he performs in what we might call the “fantasy stats.” Watch any but the most enlightened baseballing telecasts, and you will still be confronted by graphics sporting a player’s batting average, home runs, and RBIs. Along with those graphics, you’ll hear the voices of broadcasters (again, generally) quoting all the above, plus runs and stolen bases — and a whole bunch of other things, like batting average with runners in scoring position, that fail to address the real production of the player in question.

Me and you and most everyone we know are aware that a lot of those numbers are either heavily dependent on context (runs, RBI), prone to great variance in even season-long samples (batting average), or misunderstood in terms of risk versus reward (stolen bases) — and my guess is that most of us are able to mentally adjust and say, “Well, sure, he’s got a lot of RBIs, but his on-base skills are sub-par.”

This being FanGraphs, however, I wondered if it might be possible to measure how underrated a player is.

In what follows, I document my attempt to do just that.

In terms of measuring a player’s “true” value, the closest thing we have is WAR. Because batting average and defense, etc., require pretty large samples to become reliable — and because a player’s true talent is changing incrementally all the time, anyway — WAR isn’t perfect, but it does a lot of things well. For the purposes of “rating” players in this endeavor, therefore, I’ve used WAR.

In terms of measuring “perceived” value, what I did was take a player’s production in the five most-common fantasy categories (average, home runs, runs, RBIs and stolen bases) and put them on the WAR scale*. To do that, I found each player’s z-score (i.e. standard deviations from the mean) in each of those categories. I then added together the z-scores and multiplied that sum by a constant (in this case, 0.375) to give the z-scores the same range as the one on the WAR leaderboard. To each of these adjusted z-scores, I added the current (as of this past Friday, when I ran the numbers) average WAR of 1.18 (again, for qualified players only). This produced a number — I’ve called FAN — which is essentially like WAR, except it uses the five aforementioned categories. No defense. No positional adjustments. Nothing else.

*I’ve picked these numbers not because they’re the fantasy stats, necessarily. Rather, it seems the fantasy stats became fantasy stats because they were already a popular means to assessing value.

From there, I took the difference between each player’s WAR and his FAN. The larger the positive difference, the more underrated — that is, the more stuff that doesn’t show up in the fantasy categories.

Here are the results (again, including only qualified batters as of this past Friday):

Some notes:
• Positional adjustment (or the lack of it) definitely play a huge role here. On this list are six catchers, 3.5 shortstops (with Maicer Izturis being the half), and four center fielders. Of the 20 players on the list, only Jack Cust has spent much time on the right side of the defensive spectrum.

• Beyond the positional adjustment, a number of these players also appear on the UZR leaderboard, too. To wit: Span (1st, 10.9 UZR), Howie Kendrick (2nd, 7.6) and Alexei Ramirez (3rd, 7.2).

• Team context also seems to inform these rankings, as poor offenses allow fewer opportunities for scoring and for driving in runs. We see a number of players from the league’s lowest-scoring teams: Cameron Maybin (Padres), Span (Twins), Cust (Mariners), Brendan Ryan (Mariners), Ronny Cedeno (Pirates) — and Peter Bourjos, Izturis and Kendrick, who all are from the Angels.

As for the other term I invoke above (i.e. overrated), that’s a slightly different proposition. While the method I’ve employed here certainly can isolate the players whose fantasy-type numbers compare (more than) favorably relative to their WAR, it also makes sense that managers would put their best players in a position to drive in and score runs — and that players with higher averages and home-run totals would, in fact, likely have more runs scored and RBIs.

Accordingly, instead of referring to the players on this next list as overrated, we might more accurately say that they’re the least underrated players currently. It’s both a distinction and a difference, I promise.

Here: