Batting, Defense, & Baserunning: A Look at Jhonny Peralta's Value

Rick Osentoski-USA TODAY Sports

In which facets of the game does Jhonny Peralta generate value?

The St. Louis Cardinals signed free agent shortstop Jhonny Peralta to four-year, $53 million contract early in the Hot Stove. In doing so, the Cardinals upgraded at a position that was their greatest weakness (aside from third base) during a 97-win 2013 season. The Peralta signing means the Cards have replaced Pete Kozma, who derived his 2013 value solely on the base paths and with the glove with a more well-rounded player.

By now you've probably heard about the stat Wins Above Replacement (WAR). It's a stat that attempts to quantify the entirety of a player's game--batting, defense, and baserunning--in one stat. Some of the inputs into WAR are better than others. The batting and baserunning components are quite accurate. The defensive part, on the other hand, is a little bit fuzzier.

Fangraphs WAR (fWAR) uses Ultimate Zone Rating (UZR) for its defensive component. UZR is probably the best publicly available defensive metric for MLB players. But it is not particularly precise. In 2008, when Fangraphs was rolling out fWAR, Dave Cameron remarked that he generally gives UZR "an error range of five runs in either direction, meaning that a +10 could be anything between a +5 and +15." Ten runs equals one Win Above Replacement. So, fWAR could be a half-win off in assessing a player's value due to UZR's inaccuracy. And fWAR uses the best defensive metric available to the public.

fWAR also uses Weighted Runs Above Average (wRAA) for a player's batting production. This stat is adjusted for park effects before it is included in his fWAR total. Unfortunately, we don't have the park-adjusted wRAA available to us. So I've used the raw, unadjusted version in the chart.

Lastly, fWAR includes a baserunning component. It is based on Weighted Stolen Bases (wSB) and Ultimate Baserunning (UBR). fWAR accounts for a player's overall contribution on the base paths, from stealing to taking the extra base on a hit.

The following chart includes Peralta's production for the last five seasons. "Defense" reflects his UZR at shortstop only. "Baserunning" consists of his wSB and UBR. "Batting" is his unadjusted wRAA.

It's important to keep in mind that the above run values do not include two important components of fWAR. The first component not included is a positional adjustment. Shortstops receive a +7.5-run positional adjustment in fWAR. The other component not included is the park-factor adjustment for wRAA. Including these two adjustments with the above run values above gives us the following fWAR totals.

Peralta, who is entering his age 32 season, is an interesting player. Perhaps too interesting for his contract. Consider:

  • Peralta has been an up-and-down batter in recent years.
  • Peralta's defense has improved with age such that it is the lynchpin of his value as a player.
  • Peralta is a bad baserunner.

Despite these warts, Peralta has been one of the best shortstops in baseball over the last three seasons. In signing him, the Cardinals have sought to make an immediate upgrade for 2014. After losing in the World Series last season, such a win now signing makes sense. Given Peralta's volatile batting performance over the last five years, there's a legitimate a question of whether Peralta will hit enough to help the Redbirds win now.

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