Javier Baez has been one of the best and most valuable players in the National League. He’s already set career highs in doubles, triples, homers, and — most importantly — WAR, and the Cubs wouldn’t be where they are without him. At the same time, Baez has drawn a total of 17 walks, and seven of those have been intentional. He’s got 105 strikeouts. He’s swung at literally almost half of all pitches thrown out of the strike zone.

I can’t sit here and tell you whether this approach is sustainable. I mean, I suppose the approach is sustainable, but I don’t know if it can keep on leading to these same results. It’s difficult to say because we’ve barely seen any hitters like this before. It feels like Baez couldn’t possibly sustain this, but it feels just as strongly like Baez has broken out. Like he’s figured out how to best channel his aggressiveness.

What you won’t find here, then, is a conclusion. I don’t know what Javier Baez *is*. I don’t know if he’s a 100 wRC+ kind of hitter, or if he’s a 140 wRC+ kind of hitter. But I had a realization the other day, and I wanted to share some observations with you. When Baez first arrived in the majors, he was known for his Gary Sheffield-like bat speed. The question was whether he’d make enough contact, and lay off enough balls. It stood to reason that, if Baez was going to succeed, he’d have to make himself more selective. That isn’t what’s happened. Baez has leaned into his own aggressiveness, if you will. He’s hitting better than he ever has. He’s swinging more often than he ever has. Baez has become ready to hit every pitch. I’d like to show you some supporting information.

Baez has a career-high swing rate. He has a career-high rate of swings at pitches out of the zone. He also has a career-high rate of swings at pitches in the zone. For every five pitches Baez has seen, he’s offered at three of them. The differences there aren’t absolutely enormous, not relative to last season, but here’s one major change. For every player with at least 100 plate appearances in each of the last two seasons, here are their first-pitch swing rates, with Baez being the point in yellow:

A year ago, Baez swung at about a third of all first pitches. This year, he’s up around half. His first-pitch swing rate is up roughly 17 percentage points, and that’s the second-biggest increase out of 327 players, behind only Jesus Sucre for some reason. (The really weird player here is Pablo Sandoval.) That’s one way of breaking down Baez’s data. How and where, exactly, has Baez become more aggressive? More aggressive when facing first pitches. More broadly, more aggressive when there are zero strikes in the count.

In two-strike counts, Baez’s swing rate has actually gone down. In one-strike counts, it hasn’t budged very much. In zero-strike counts, it’s way up. Baez has made a point of trying to attack earlier on. He was already aggressive before, but in zero-strike counts in 2017, his swing rate ranked in the 86th percentile. In zero-strike counts in 2018, he has the highest swing rate in either league. Baez has been trying to ambush the competition, and it would be hard to argue it hasn’t worked. While he’s certainly not walking, he does have his strikeouts under control, and he leads baseball with 31 extra-base hits in zero-strike counts. The next-closest batter has 26. Baez is on track to finish with one of the higher totals we’ve seen since pitch-by-pitch data started being recorded in 1988.

So we can see where Baez has turned it up. He’s been trying to do more damage early on, before pitchers feel comfortable really expanding. To narrow down, however, it’s really fun to look at what Baez has done against curveballs. He’s never swung at so many curves before. This is a fact: For every four curveballs Baez has seen in 2018, he’s swung at just about three of them. How absurd is that kind of curveball swing rate? Here’s the present-season leaderboard:

Here’s the leaderboard going back to 2008:

2008-2018 Curveball Swing Rates Player Year Swing% Javier Baez 2018 73.2% Vladimir Guerrero 2010 70.8% Rajai Davis 2010 66.3% Carlos Gomez 2012 65.7% Delmon Young 2013 65.6% Carlos Gomez 2015 65.0% Vladimir Guerrero 2011 64.8% Torii Hunter 2008 64.5% Josh Hamilton 2012 64.3% Carlos Gomez 2017 64.2% SOURCE: Baseball Savant

No one else has been this aggressive against curveballs. Only 2010 Vladimir Guerrero finished with a swing rate north of 70%. Baez’s lead in 2018 alone is massive, and — well, maybe this will surprise you, or maybe it won’t. What’s been driving Baez to go after so many curves? He’s been tremendously successful. Here’s the 2018 leaderboard for top run values against curves:

And now here’s the leaderboard going back to 2002:

Baez has been obliterating curveballs. He’s been the most productive curveball hitter in 2018, and at least by this measure, he might be the most productive curveball hitter since at least 2002. It feels a little weird to zoom in on one particular pitch type, since curves aren’t the only pitches with spin, and this is also a stat that’s subject to noise. But through 2017, Baez, against curves, had a career run value of -10.7. This year, against curveballs, Baez has 28 hits, 17 for extra bases. Through the end of last year, against curveballs, he had 28 hits, nine for extra bases. One way to interpret this is that a lot of pitchers will try to use their curveballs to steal a strike. Baez hasn’t been allowing that to happen.

Here’s what Baez did to a first-pitch curveball the other day:

The next time up, another first-pitch curve:

The following day, a first-pitch (possible) curve:

For whatever reason, 2018 Javier Baez has feasted on curveballs. He’s swung at them more often than ever before, and he’s made easily his best-ever contact. At the same time, he’s remained ever so dangerous against heaters. Baez has made a point of attacking early in counts, maybe because it’s too early for most pitchers to try to throw their best chase pitches. Baez still gets in trouble when pitchers are ahead. His strategy seems to be to prevent them from getting ahead in the first place. He’s been ready for fastballs and ready for curves from the first pitch of any at-bat, and it can be a psychological struggle to pitch to a guy you know can take you deep if you throw the ball anywhere around the zone.

It still feels like Baez’s approach should be somehow exploitable. It still feels like he’s way too aggressive out of the zone. But baseball’s probably more fun if that isn’t the case. If Baez doesn’t fit in any of the categories we already had, that means there’s a new category to make. That means we’d all still be learning, even after all of this time.