Carlos Correa’s Rookie Season Hints at Greatness

The 2015 season has been chock-full of high-profile rookie debuts. From Kris Bryant to Corey Seager to Noah Syndergaard, I’ve certainly had no shortage of players to write about. But the most impressive rookie campaign — at least on a per-game basis — might very well belong to Carlos Correa, who’s developing into a superstar right before our eyes. Although he’s completed just his age-20 season, Correa’s been one of the best better hitters in the game since the Astros called him up on June 8th. His 133 wRC+ was the 28th best among hitters with at least 400 plate appearances this year, and second best among rookies, trailing only Kris Bryant. By the barometer of WAR per 150 games, Correa ranked 21st in baseball with mark of 5.2.

You probably didn’t need me to tell you that Carlos Correa’s been really good. This isn’t exactly news. So rather than dwelling on how good Correa is now, I want to consider what his impressive rookie campaign means for his short- and long-term future.

I’ll start off by looking at what he did in his two months in the minor leagues. Correa opened the year at the Double-A level, where he hit an absurd .385/.459/.726 in 29 games before the Astros bumped him up to Triple-A. I wrote about Correa at the time of this promotion, and unsurprisingly, the data had glowing things to say about his long-term outlook. Based on his Double-A performance, the names Mike Trout, Cliff Floyd and Asdrubal Cabrera  showed up as statistical comps, putting him in some mighty fine company.

His stay at the Triple-A level was short lived, as the Astros called him up to the show after just 24 games. His .276/.345/.449 showing at the level was a few notches down from his Double-A performance, but still very impressive for a 20-year-old shortstop. Based on his Double- and Triple-A numbers, KATOH pegged him for 19 WAR through age 28, which was tops among players with at least 200 plate appearances in the minors. Before he even stepped on to a big league field, Correa had the statistical track record of a star in the making.

Now, I’ll look at the more important part of Correa’s 2015 campaign: his big league performance. The crux of this exercise revolves around Correa’s statistical comps, which were calculated by way of some weighted Mahalanobis distance calculations. As a warning, the next couple of paragraphs will be strictly about math. If you’re more interested in reading about Carlos Correathan you are in reading about math, feel free to skip ahead to the table of comps.

First, I took every rookie season since 1955 in which a hitter aged 19-21 recorded at least 400 plate appearances. Then, I turned every possible offensive outcome into a rate stat, regressed them for sample size and scaled them to league average. In my distance calculations, I applied weights to each of these rates based on the 2015 wOBA coefficients in order to properly weigh the importance of each component. In simpler terms, I compared Correa’s rookie season to other young players’ seasons by weighing each metric according to its offensive importance.

One tweak, though. While wOBA does a good job of quantifying a hitter’s past performance, it fails to account for some things that fall largely outside of a hitter’s control. Most notably, it does not adjust for BABIP. In other words, it treats all outs equally whether they’re strikeouts, line drives or otherwise, which is less than ideal when trying to predict the future. So, I also threw strikeout rate into the mix. I gave it the same coefficient as walk rate, since my KATOH models revealed that a hitter’s strikeout rate and walk rate in Triple-A have similar predictive power.

Enough technical mumbo-jumbo! Let’s have a look at Correa’s top comps based on my fancy computer math. Here are the players whose rookie campaigns most resembled Correa’s.

And let’s see how the rest of their careers turned out.

Career Stats for Carlos Correa’s Mahalanobis Comps

Name	wRC+	WAR
Cal Ripken	112	92.5
Ken Griffey Jr.	131	77.7
Eddie Murray	127	72.0
Gary Carter	116	69.4
John Olerud	130	57.3
Jason Thompson	123	27.1
Curt Blefary	117	12.1
Tony Conigliaro	119	11.8
Carlos May	112	9.4
Eric Hosmer*	108	6.1

*Career still in progress.

On the whole, their careers turned out pretty well. Ripken, Griffey, Murray and Carter are all Hall of Famers, while Olerud was one of the best hitters in baseball for a time. Conigliaro might have been right up there too had he not suffered a career-derailing injury at age 22. In a nutshell, Correa is keeping some pretty good company. Here’s a look at these hitters’ career trajectories by cumulative WAR.

And by marginal WAR.

There are lines going in every which direction in that last chart. You probably noticed that a few of those lines approached the 10 WAR mark at various points, but other than that, it’s a little hard to grasp what’s going on. So let’s try a simpler graph that doesn’t look so much like spaghetti. The graph below plots the group average and median, along with the group’s 25th and 75th percentiles for each year.

The outlook here is pretty encouraging. This group’s mean bounces between 3 WAR and 5 WAR, with a modest upward trend. A perpetual four-win player pretty darn good. However, it’s those top two lines that should really make you giddy. One out of every four hitters topped the 4.0 WAR mark in just about each season, while at least one eclipsed 7.0 WAR.

Correa had one heck of a rookie campaign, and was a big part of the Astros’ unanticipated run to the playoffs. But most remarkable of all, he did almost all of it as just a 20-year-old. He’s still a baby by baseball standards — and by many non-baseball standards, for that matter. Still, in spite of his youth, he very well might be the most talented player on the field in tonight’s wild card game. He’s already that good; and hitters who are that good at 20 are often great in just a few years’ time.