Is Carlos Correa Baseball's Most Productive Shortstop?

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"I don't think I was successful this year offensively. I don't think my year was that good. This offseason, I need to work at some things and get better and have a better year next year." --Carlos Correa quoted in Oct. 2 mlb.com article

Let me say, first of all, that I love the attitude expressed by Carlos Correa.  Great players place high expectations on themselves.  Astros' fans look forward to even greater offensive proficiency from Mr. Correa.   But the author of the article, Brian McTaggert, suggested--correctly--that Correa was being hard on himself.

I would argue that Correa had a very good season of offensive production.  Depending on how you measure it, Correa arguably was the most productive offensive shortstop in baseball.  Maybe Carlos would like to be the most productive offensive player, regardless of position.  Again, that's a great attitude.

Let's focus on sabermetric measures of Correa's offensive production.

Linear Weights Metric

wRC+ is one of the best linear weights measures of offensive performance.  Linear weights metrics assign an average value or weight to each single, extra base hit, and walk; the intent is to reflect the average contribution to run creation for each of those events.  wRC+ is set out as a ratio of average major league run creation, with 100 equivalent to a league average hitter.  Based on wRC+, Correa had the third best offensive performance among shortstops in 2016.

1. Corey Seager 137

2. Manny Machado 129

3. Carlos Correa 122

I might put an asterick by Machado on this listing of shortstop production, because he primarily played 3d base.  However, when J.J. Hardy was injured, Machado played shortstop enough to qualify for the fangraphs' shortstop list.  Furthermore, if we are interested in actual offensive production, wRC+ isn't the most direct measure.  wRC+ is context neutral, and the actual run production depends on situational context.  wRC+ is based on average run production across all situations.  Some players achieve greater than average run production from a given set of offensive events.  Perhaps wRC+ is more repeatable (or regressed) than actual results--and, therefore, more useful for forward-looking purposes.  But if our focus is on a player's actual run production, context-based stats may be useful.

WPA and RE24

The Win Probability family of stats provide context-based results.   WPA is win probability added.  RE24 is run expectancy for the 24 base-out states; RE24 and REW are the same thing, except REW converts the RE24 runs to wins.

WPA is based on the change in win expectancy (probability of winning the game) due to a player's offensive actions. Season ending WPA is cumulative of the player's positive and negative contributions to winning each game.  WPA is highly dependent on the leverage (game score and inning, as well as base-out situation) at the time the player batted. For that reason, WPA places much more value on a solo HR in the 9th inning of a close game than a solo HR in the first inning of the same game.  Thus it may be dependent on sequencing luck, which is why WPA isn't favored as a metric for measuring players' talent.  However, WPA is an accurate measure for describing why games were won or lost.  In that sense, WPA does reflect actual contributions to wins, whether due to luck or skill.

If you define offensive production as actual contribution to wins, then Carlos Correa was the most productive shortstop in 2016.  The top five are shown below.

"Repeatable" stats are frequently measured by the correlation of the metric from year-to-year. By this measure, WPA is somewhat repeatable from year-to-year,but  not as much as some context neutral stats like OPS and SLG.  One reason for the yearly correlation is that very good offensive players tend to achieve higher WPA simply because they are good hitters; for example, the 2016 WPA leaders, regardless of position, are Mike Trout, Josh Donaldson, and David Ortiz, all of whom are MVP candidates.

RE24 (and its twin, REW) is similar to WPA, but measures run expectancy rather than win expectancy.  RE24 eliminates the impact of game score and inning components of WPA.  As a result, RE24 measures situational context but is more repeatable than WPA. RE24 correlation from year-to-year is similar to linear weight methods, like OPS.  For each plate appearance, RE24 measures the extent that a player exceeded or fell short of the average run expectancy associated with the base-out state.  (Example of base-out state: runner on 1st and 2d with 1 out, which has a run expectancy of 0.9 runs.)  A player's placement in the batting order will affect the opportunities to accrue more positive or negative RE24, but this reflects the reality that production is related to run scoring opportunities.

I have previously discussed RE24 in this article, and Joe Posnanski writes here about the usefulness of RE24 in settling MVP debates.  My article points out that Jeff Bagwell, Lance Berkman, and Craig Biggio are the Astros' career leaders in RE24.  Posnanski mentions that Barry Bonds led the league in RE24 ten times, and Mickey Mantle led the league eight times.  An advantage of RE24 is that it reflects the specific effects of events like GIDP, strike outs, and productive outs which are not part of most linear weights methods.

Based on RE24, Correa topped AL shortstops, and he was second to Seager among all shortstops. The top five are shown below.

In 2016, Seager and Correa were 1 and 2 in offensive production among shortstops, and their ranking as 1 or 2 depends on whether it is based on win expectancy or run expectancy.

This Decade's Shortstops

Since Correa has almost 1,100 plate appearances in the majors between 2015 and 2016, he is among the qualified shortstops on fangraphs leaderboard for 2010-2016.  Just for fun, we can compare Correa's offensive production to the top shortstops of this decade.  Starting out with the linear weight-based wRC+, Carlos Correa is already the second ranked shortstop among qualified shortstops 2010-2016.

Turning next to the more context-based WPA and RE24 (REW), Correa is No. 4 (for both metrics) among shortstops on the 2010-2016 leaderboard.  But WPA and RE24 are counting stats, and the plate appearances vary widely for qualified shortstops in the period 2010-2016.  Therefore, I converted REW to a rate stat per 1,000 plate appearances.  Based on this approach Correa's offensive production compares favorably to the top five REW qualified shortstops on the 2010-2016 fangraphs leaderboard.

On a rate basis, Correa has the highest REW among the decade's best offensive shortstops.  Correa's actual run contribution has outperformed his linear weight-based results. We can evaluate the extent that his REW exceeds the average performance embedded in the linear weights by comparing RE24 results with weighted runs above average (wRAA).  For Correa, RE24 results are approximately 38% higher than the wRAA (47.9 RE24 vs. 37.8 wRAA).  The "added value" reflects higher run values for hits and walks, as well as the ability to avoid excessive negative impacts from double plays, strike outs, and non-productive outs.  As discussed in my previous article on RE24, Bagwell, Berkman, and Biggio all added run expectancy value in excess of their wRAA--by margins of 17% - 52%.

You may think this is statistical overkill.  But here is the reason to be impressed: Carlos Correa was 21 years old this season.  He has already put his name up there with the most productive shortstops of the decade.  Yet he is still quite young. The comparisons of Correa and Alex Rodriguez are sometimes overdone. That said, Correa and A-Rod produced almost exactly the same REW through their age 21 seasons. Given the probable continued maturation of hitting skill and power over the next few years, at this point we may have  seen only a glimpse of his offensive ability.