Willi Castro: Rookie Sensation

MINNEAPOLIS, MINNESOTA - SEPTEMBER 22: Willi Castro #49 of the Detroit Tigers makes a play at shortstop to get out Ryan Jeffers #39 of the Minnesota Twins at first base during the eighth inning of the game at Target Field on September 22, 2020 in Minneapolis, Minnesota. The Twins defeated the Tigers 5-4 in ten innings. (Photo by Hannah Foslien/Getty Images)
MINNEAPOLIS, MINNESOTA - SEPTEMBER 22: Willi Castro #49 of the Detroit Tigers makes a play at shortstop to get out Ryan Jeffers #39 of the Minnesota Twins at first base during the eighth inning of the game at Target Field on September 22, 2020 in Minneapolis, Minnesota. The Twins defeated the Tigers 5-4 in ten innings. (Photo by Hannah Foslien/Getty Images) /
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Detroit Tigers shortstop Willi Castro is having a terrific rookie season. Let’s look at what’s fueling his success, and see if it will last.

Willi Castro had another strong game last night, going 2-for-4 with a walk, hitting a go-ahead single in the 7th, and playing solid defense at shortstop. It was his 11th multi-hit game of the short season, and his .336/.374/.531 batting line gives him a 144 wRC+, which is tied with Jeimer Candelario for best on the Tigers.

Castro ranks 4th among Tigers hitters with 1.0 fWAR, and he’s also 4th among American League rookies in fWAR. He’s not going to win Rookie of the Year, but he may get some down-ballot votes. We gave him a B on our Rookies Progress Report, but it’s hard to imagine him not finishing with an A after the season.

By any objective measure, Willi Castro has had a great rookie season. But how does it compare to recent Tigers rookies?

Willi Good

Willi Castro’s 2020 season is the 11th best rookie campaign by a Tigers hitter since 2000, at least according to FanGraphs. That’s solid, but not particularly special. But we do have to remember one thing: Castro has played in just 32 games this season. If he maintained this pace for a full season he’d be close to a 5-WAR player!

Things never work out that way, of course. Castro owns a ridiculously high .440 batting average on balls in play, and he’s striking out too much while not walking enough. That’s a recipe for a pretty huge regression once pitchers figure out how to attack him — though his .292 expected batting average is still pretty strong.

Let’s see how Castro’s 2020 season compares to the first 32 games from the rest of our 21st-century Tigers rookies:

First 32 Games

Castro is off to the 4th or 5th best start by a Tigers rookie since 2000. That’s pretty impressive, but Tigers fans might recall how swiftly Berry and Boesch crashed back to earth. Austin Jackson somehow maintained a .396 BABIP for the whole year and finished with a terrific 4.1 WAR season, aided by outstanding defense. Speaking of D…

Put a Glove on that Willi

One big concern with Willi Castro has been his defense, specifically, the accuracy of his throws:

That’s not great, and it has been an issue for Castro for a few years now. He’s -3 outs above average at shortstop according to Statcast, he has -5 defensive runs saved according to Fielding Bible, and, as you can see in the table above, FanGraphs also grades him as a negative defender.

Defensive metrics are famously unstable, but if multiple systems have him as a negative with the glove, we can probably assume he’s a poor defender. Rookies are bound to have some deficiencies, and the Tigers can put up with Castro’s bad defense as long as he posts a 144 wRC+.

But we know Willi Castro’s offense is going to regress in the future, so if he wants to stay valuable he’ll need to pick it up on defense. He has at least looked better on defense over the last few weeks, and he definitely has the tools to play the position:

Speaking of tools…

Power and Speed

Willi Castro has one of the more impressive mixes of power and speed among this year’s rookie class, but he’s not really taking advantage of his tools yet. The raw numbers aren’t particularly inspiring — out of 49 qualified rookie hitters, Castro ranks 9th in home runs, 14th in isolated power, 42nd in baserunning, and he has no stolen bases.

But the underlying metrics tell a different story. Castro’s sprint speed of 28.2 ft/sec ranks in the 86th percentile among all players this year, and only three rookies have hit a home run farther than his 445-foot bomb on August 22nd.

Castro is one of just ten players this season with an average sprint speed of at least 28.2 ft/sec and a home run of 445 feet or longer, joining Ronald Acuna Jr., Trent Grisham, Starling Marte, Adalberto Mondesi, Luis Robert, Trevor Story, Fernando Tatis Jr., Chris Taylor, and Mike Trout. That’s elite company.

Conclusion

Tools alone don’t mean Willi Castro will be an average MLB player. His ugly baserunning numbers and poor defense may be indicative of bad instincts, and his aggressive approach could limit his power production. But Castro has definitely had a strong rookie season, and it looks like he has the potential to be even better.

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