Lucas Erceg has been…something less than good so far this year.

When the Royals traded for him in 2024, he immediately became the team’s best reliever and locked down the closer role. More than that, though, he seemed like a shutdown reliever in the vein of Kelvin Herrera, Wade Davis, and Greg Holland. It’s almost impossible to have three relievers of that quality at the same time – the Dodgers tried and ended up with bupkis last year – but a team with playoff aspirations probably should have at least one of them*, and Erceg figured to be the Royals’ answer to that need after his terrific debut.

*Though, again, look at the Dodgers. Sometimes, you can get by with a really good starting pitcher who is willing to do crazy things.

Unfortunately, since the end of 2024, Erceg has simply not been the guy the Royals hoped for. In a lot of ways, he appears similar, and he still had a 2.64 ERA last year. But this year, through the season’s first month, he’s wielding a 4.38 ERA and, even more concerning, he has a 5.36 SIERA, suggesting that he may actually have been lucky to pitch even that well. So what the heck is going on?

There are two primary theories I considered: either he’s tipping pitches, or he’s throwing too many non-competitive pitches. Now, normally, the first place you should go to research a pitcher is TJStats.ca. It’s a fantastic website with gobs of data that takes what’s present on Baseball Savant and expands on it, but also makes it easier to comprehend. If you’re willing and able to pony up for a subscription, you can get even deeper analysis. Fortunately for you all, I’ve traded in some of my Pop-Tarts, and so I can offer you this comparison image of Lucas Erceg in 2026 and 2024.

Now, if you just go to the bottom row of the pitch tables, he doesn’t seem all that different. He’s throwing nearly as many strikes as before, and the xwOBACon (a stat that estimates how much damage should have been done based on contact quality) is pretty similar to 2024. But the chases and whiffs are WAY down. That would seem to be a point in favor of pitch tipping. But hold on a second… let’s look at things pitch by pitch. He’s actually throwing far more strikes with his sinker and changeup than before, but missing with his four-seamer and slider at truly awful rates for those pitch types. The problem is especially bad with his slider.

So I decided to do an extra deep dive in the slider. I went on Baseball Savant, and I watched literally every slider he’s thrown this year, and I came to an incontrovertible conclusion. The problem isn’t that he’s tipping pitches, and it’s not even that he’s not throwing his slider in the zone often enough. It’s that too few of his sliders ever even look like strikes.

Location, location, location

There’s a concept in pitching where you can describe the movement of a pitch by whether it starts as a strike or ball and ends as a strike or ball. So, if a pitch appears to be a strike upon release and ends up outside of the strike zone, that would be called a strike-ball pitch. Vice versa is ball-strike. And in the same vein, you can describe a pitch as a strike-strike or a ball-ball. This description format shows its weaknesses for some kinds of pitches, of course:

That pitch is technically a ball-ball. But it would be better described as a ball-strike-ball. It starts off outside, passes through the area that would be the strike zone if the strike zone were a cylinder, and then ends up low. For the purposes of today’s discussion, I classified such pitches as strike-ball pitches because I was primarily concerned with whether the batter had any reason to consider swinging. If you’re curious, he only had one other ball-strike-ball pitch.

Far too many of Lucas Erceg’s sliders are ball-ball pitches. He has thrown a total of 65 sliders so far this year, and 49 of them have ended up outside the zone. Now, sure, he should probably throw a few more in the zone. But by far the biggest problem is that, of the 49 sliders that have ended up outside the zone, 25 of them look a lot like this:

This has led to only one swing and one check swing on those pitches. Which makes sense. A slider succeeds based on its ability to convince a batter that it’s a fastball before diving off course. But those 25 pitches start off outside the strike zone, so batters don’t even really need to consider whether they might be fastballs or sliders. And the one swing he got was Gunnar Henderson on a pitch that looked like it was headed back toward the zone*:

*One thing I discovered during this process is that Erceg has two different slider actions. You’ll note that this one is breaking back armside, sometimes referred to as a wrong-way slider or a goofy slider. That’s why, if you refer back to Erceg’s comparison tables, it looks like his slider does break horizontally, it averages out to near nothing because some of them break glove-side and some break arm-side. This is neat and weird, but it has always been true of Erceg, so it isn’t the cause of his current troubles.

On the other hand, of the 24 sliders Erceg has thrown strike-ball, he’s gotten swings on 12 of them, along with 3 check swings. Of those swings, only two have been put in play, and three have been fouled off. So if you could reduce his sliders to just the ones he’s thrown strike-ball, he has a 50% chase rate and a 58.3% whiff rate. Those are staggeringly good numbers. He doesn’t need to throw more sliders in the zone to succeed; just more sliders that look like they might be strikes.

It turns out there’s nothing wrong with his slider’s deception, just his accuracy. Now, unfortunately, I can’t tell you why he’s throwing so many non-competitive sliders. It could be a mechanical issue, but if it were, I’d expect to see them consistently missing in the same way; instead, some of them end up spiked while others end up looking like something Ricky Vaughn would throw.

It could be that he’s afraid of hanging them in the zone, so he’s making sure to miss out of the zone if he misses at all. But, as you can tell from the graph earlier, he really doesn’t seem to need to worry about batters making contact. A. 158 xwOBACon is fantastic. Overall, his average exit velocity against is 88.8 MPH with an average launch angle of 8 degrees. In other words, the most likely batted ball you’d expect is a routine groundout. He’s only given up 10 hits in 12.1 innings, it’s the 10 walks in the same span that have often doomed him.

He’s only given up two hits on sliders this year, weirdly, both against Milwaukee on April 5. Meaning he hasn’t given up a hit on a slider outside that game. The first was a center-cut slider that resulted in a 94-MPH line drive off the bat of Jake Bauers with an XBA of .510 that Bauers turned into a hustle double. Basically, he threw the worst slider he could, the batter put a really good swing on it, and he still probably should only have given up a single, if that. The second was his other ball-strike-ball slider; Brandon Lockridge managed to bloop it into center and scored an RBI single on a ball with an XBA of only .350. A coin flip and a 1-in-3 chance are the best anyone’s been able to get off of Erceg’s slider when he lets them make contact with it.

The fix is simple, though if it were easy, I imagine he’d have done it by now. Lucas Erceg just needs to get his sliders aimed at the strike zone. If he could do that more often, he might immediately return to being the Lights Out Lucas we remember from 2024.

Here’s hoping he can figure it out soon.