I have been monitoring the effects of Baseball Prospectus’ recent modifications to its wins-above-replacement metric, WARP, on Miguel Cabrera’s career valuation numbers, and, on the whole, the results for Cabrera have been positive.
On Monday, former Baseball Prospectus editor in chief Ben Lindbergh discussed the ways in which WAR metrics always are in some state of flux as they incorporate newly available information and adapt to significant changes in game strategy and play:
In a sense, it’s unsettling that WAR is always in motion. Batting average may not be an accurate indicator of overall (or even offensive) value, but barring an overturned ruling by an official scorer or an unearthed error in archaic records, it always stays the same. Ted Williams will always have hit .406 in 1941, but his FanGraphs WAR for that season was 11.9 in 2011, and today it’s 11.0. That’s one reason why WAR values may never achieve the emotional resonance of evocative stats such as .406, 56, or 755, or even milestones like 3,000 hits or 500 homers.
WAR reminds us that objective truth tends to be slippery. And the metric is likely to get more unstable before it someday settles down. None of the big three versions of WAR(P) currently incorporates Statcast data. Thus far, MLBAM has drawn on that data to quantify aspects of player production without generating one unified number, but Tango describes it as “inevitable” that “eventually they will get rolled into one Statcast WAR metric.” He acknowledges that WAR’s amorphousness may make some fans more hesitant to trust it. Even so, he says, “Our focus should be on representing the truth as best we can estimate it. And it’s the truth that will attract the people.”
Baseball-Reference founder Sean Forman has responded to criticism of WAR’s mutability—not to mention its multiple implementations—by comparing it to Gross Domestic Product (GDP), another complex statistic that also changes retroactively and comes in more than one form. WAR works the way all science does: Discoveries are scrutinized, assumptions are examined, errors are rooted out, and breakthrough by breakthrough, we learn.
The focus of Lindbergh’s article was on the ways in which teams are straying from the traditional sequencing of starting and relief pitchers– frequently referred to as “the opener” strategy– are affecting WAR calculations, particularly Baseball-References bWAR.
An obstacle I encountered in analyzing changes in Cabrera’s WARP is that BP doesn’t keep a public record of statistical changes. By contrast, as Lindbergh helpfully noted, B-R does keep a public bWAR index, which effectively permits the tracking of changes to individual players’ seasonal bWAR totals on a daily basis since March 29, 2013.
In light of my prior documentation of the recent set of changes to Cabrera’s career seasonal WARP totals, I decided to take a quick and very rough look at how Cabrera’s seasonal bWAR totals had changed over the last six years. What I found was that, at least through 2012 (covering the first ten years of his career, which was all that was included in the March 29, 2013 data set), the difference was negligible. Some years’ bWAR numbers had increased a bit, some had decreased a bit, and some didn’t change; in total, the aggregate difference was -0.13 bWAR over those ten seasons. Doing a similar thing for the next six seasons by using the bWAR value from the first available date on the calendar year immediately following the completed season yielded a similar mix of results, with an aggregate difference of +0.38 bWAR. Combined, the total change is an increase of 0.25 bWAR, basically a negligible amount. Coincidentally, “negligible” also describes the value over replacement blog post (VORBP) of what you’ve just read.