What Has Happened With Lucas Erceg?

 The Royals' nightmare stretch and season continued on Saturday afternoon in Arlington. 

Despite leading 6-4 in the bottom of the ninth, Royals closer Lucas Erceg gave up three runs on five hits to blow the game to Texas. Ezequiel Duran had the game-winning single that scored Brandon Nimmo from third base with no outs.

After closing out the game against the Cardinals on May 17th, Erceg has given up eight runs on 13 hits in three appearances. His ERA has risen from 3.26 to 6.33 over that three-game span, and his WHIP has risen from 1.45 to 1.92. Overall, it's been a challenging season for Erceg, as he has not just struggled to generate whiffs and strikeouts, but has also posted a career-worst wOBA, as illustrated in his TJ Stats percentiles below.

The percentiles aren't pretty in many categories. 

According to TJ Stats, Erceg ranks in the 27th percentile in K%, 19th percentile in O-Swing% and Whiff%, 15th percentile in Strike%, 13th percentile in BB%, 8th percentile in wOBA, and 2nd percentile in CSW. He has done a good job of maintaining strong numbers in average EV on batted balls (77th percentile), GB% (79th percentile), and fastball velocity (87th percentile). Unfortunately, those positives have been overshadowed by the negative categories.

For comparison, here's what Erceg's TJ Statcast summary looked like back in 2024, when he helped lead the Royals to the ALDS after coming over from Oakland at the Trade Deadline.

As Royals fans can see, Erceg had only two categories below the 50th percentile in 2024 (swing% and zone%). He had all the characteristics of an elite reliever in 2024. While things regressed a little in 2025, he was still much better in many categories last season, especially in wOBA, O-Swing%, and BB%, as illustrated below.

So what has happened to Erceg in 2026? Why has he declined so dramatically since 2024 and become so unproductive in the late innings this season?

A lot can be tied to his regression in TJ Stuff+ and to the command of his pitch arsenal, especially with two key pitches.

Erceg's TJ Stuff+ Has Declined  Heavily Overall Since 2024

When it comes to a pitcher declining in production from one season to the next, a drop in velocity is often highlighted as the primary culprit. That was the case with Carlos Estevez, who went from throwing in the upper 90's to under 90 this season. 

Unfortunately, that's not the case with Erceg. His velocity, on all of his pitch types, has remained pretty similar to previous seasons, as illustrated by his pitch velocity chart by season below, via Baseball Savant.

Yes, there's a small decline in velocity this year, but it's not enough to be alarming. For context, here's a look at Estevez's average pitch velocity chart over his career.

That's a pretty sharp decline for Estevez and a sign that something was seriously wrong (as a result, he's on the IL, and it's unlikely that he will return this season). As for Erceg, the decline in velocity is evident, but it's not excessive or a massive outlier from previous seasons. 

That said, there's more to a pitch's effectiveness than just velocity. Movement, spin rate, and release point are key, and the quality of those characteristics of a pitch can often be measured with various pitch-tracking tools, including TJ Stuff+, created by Thomas Nestico, the founder of TJ Stats. 

For those unfamiliar, TJ Stuff+ can be defined as follows, per TJ Stats' website.

Quote

tjStuff+ is an advanced baseball pitching metric created by data scientist Thomas Nestico (founder of TJStats). It evaluates a pitcher's raw physical abilities, specifically measuring the expected run value (xRV) of individual pitches based on mechanics like velocity, movement, spin rate, and release point.

When it comes to TJ Stuff+, Erceg has seen a massive regression in his pitches compared to 2024, as illustrated in his TJ Stuff+ summary below, which shows the differences in certain categories from two seasons ago. 

Here is a breakdown of the declines on all of the pitches in his arsenal from 2024.

• Four-Seamer: Seven-point decline.
• Slider: Four-point decline.
• Sinker: 10-point decline.
• Changeup: one-point decline.
• Overall: Six-point decline.

The decline in overall TJ Stuff+ has led to regression in many important categories. His chase rate is down by six percent, and his whiff rate is down by 10.6%. The change in zone and xwOBACON has been minimal, with differences of -0.1% and +0.006%, respectively. 

For a more complete breakdown of the difference from 2024 to 2026, here is a complete comparison of his TJ Stuff+ summaries from 2024 to 2026, which also includes the difference in pitch break from 2024 to 2026.

There doesn't seem to be a whole lot of difference in his pitch break chart. The arm angle has a one-degree difference, but the pitches break this year move similarly to how they did in 2024. That said, we do see the TJ Stuff+ and grades from 2026 sport major differences from 2024. 

In 2024, Erceg had an overall TJ Stuff+ of 106, two pitches with grades over 70, and no pitches with grades under 54. This year? He has a 100 overall TJ Stuff+, no pitches with grades of 70 or over, and only two pitches with grades over 50 (sinker and changeup). In terms of vertical and horizontal movement, the four-seamer has less iVB (induced vertical break) this year, and the sinker has MORE iVB. The slider also has more HB (horizontal break) than two years ago, and the spin is down on all four of his pitches.

Those movement changes, combined with subtle regression in velocity, have seemed to make the TJ Stuff+ on Erceg's pitches more mediocre this year. That lackluster TJ Stuff+ has resulted in chase and whiff rates under 30% this year, a big drop from the 30+% marks he had in those categories two seasons ago.

The Sinker and Slider Are the Main Concerns

What made Erceg so effective as a reliever was that he had two premium pitches: the sinker and slider. 

In 2024, the sinker had a 72 grade (109 TJ Stuff+), a 30.6% chase rate, a 21% whiff rate, and a .211 xwOBACON. The slider had a 54 grade (105 TJ Stuff+), a 34% chase, 37.5% whiff, and .283 xwOBACON. 

When sequenced together and located effectively, the pitch combo could be absolutely nasty. Below is a compilation of clips of Erceg generating whiffs with the sinker and slider back in 2024 against the Yankees' Juan Soto and the Reds' Stuart Fairchild. 

 

To break down Erceg's sinker and slider further, let's utilize his pitch heatmap summary data from those two pitches via TJ Stats. That could give us an idea not just of where those pitches were located, but also of the metrics derived from that heatmap data.

Here's a look at the sinker heatmap data.

Erceg was pretty consistent with his location of the sinker, keeping it arms side and down against both lefties and righties. It was more of a weapon against righties, as evidenced by his 39.8% usage against righties compared to a 3.6% usage against lefties. However, it was equally effective against both sides of the plate. Against lefties, he had a 35.3% CSW and .217 xwOBACON. Against righties, it had a 28.1% CSW and .210 xwOBACON. When he wasn't generating called strikes or whiffs, he was limiting hard contact, which is what one wants to see from a sinker.

Now, let's take a look at the slider heatmap data.

Erceg distributed the slider more evenly against hitters. It had 24.3% usage against lefties and 31.6% against righties. Against righties, he focused more on locating the pitch low and away, while against lefties, he was more willing to be spread out in his location. The pitch was a great CSW pitch against both sides of the plate, with a 34.5% mark against lefties and 34% mark against righties. However, against lefties, it produced better chase (40.3% O-Swing to 29.1% O-Swing against righties) and xwOBACON (.128 against lefties; .372 against righties).

Now, let's take a glance at the sinker heatmap data this season for Erceg.

The biggest difference with the sinker is that he's throwing it WAY more in the heart of the plate against both lefties and righties. In 2024, the heart% was 35.3% against lefties and 27.6% against righties. This year? Those percentages are 42.4% against lefties and 37.9% against righties. That's a difference of 7.1% and 10.3%, respectively. While it's important to throw strikes with the pitch, Erceg is leaving the sinker too much in the middle of the zone.

And what happens when a pitcher leaves it in the middle of the zone too much? It gets hit. The xwOBACON is .272 against lefties this year, which is higher than the .217 mark in 2024. Against righties, the xwOBACON is good, but his 15.4% whiff rate is down from 21.7% a season ago. The sinker is profiling better than his four-seamer, but it's not quite the elite pitch that it was back in 2024.

The same is true with the slider, as illustrated by the heatmap data via TJ Stats.

The slider heatmap location has been much different this season compared to 2024.

The heatmap is totally different on the left side: he is throwing fewer pitches in the heart% zone, but the lower pitch location has led to fewer whiffs and chases. Because Erceg's slider was so diverse in terms of location to lefties, it had a 34.5% CSW, 37.5% whiff, and 40.3% O-Swing% in 2024. This year? He has a 12.5% CSW on the slider, 17.6% whiff rate, and 19.4% O-Swing%. Those are significant differences and make the pitch far less effective against lefty hitters.

Below is an example of a 0-2 pitch this season against Milwaukee's Christian Yelich that Yelich spits on because it misses the zone so badly. Because lefties are keen that it's not going to be in the middle of the zone, they tend not to respect the slider, even in pitcher-friendly counts.

 

Now let's take a look at 2024, where Erceg can get Andres Gimenez swinging on a two-strike slider. It's located more on the edges of the strike zone, and it's a harder, sharper offering. That makes it a lot tougher for hitters to lay off, especially in two-strike counts. 

 

Erceg, struggling with that sinker-slider command, with the latter particularly against lefties, has been a big reason he's not generating CSW or chase in 2026 and has led to his lackluster numbers overall this season.

What To Do With Erceg Going Forward?

Right now, I wouldn't be surprised if Erceg hits the IL with an injury. We have seen a trend where relievers with bad stretches end up going on the IL with some kind of issue or ailment. It happened with Estevez, Matt Strahm, and Nick Mears. Considering how poorly Erceg has pitched recently, it wouldn't surprise me if the same fate befalls him.

At the same time, Erceg's issues are command-related, not stuff-related. The stuff is fine, though I would like to see his slider be a sharper, harder offering than the loopy one it has become this year. He could work on that in lower-leverage work, whether at the Major League level or in Omaha on a rehab stint.

Regardless, Erceg probably needs to be out of the closer's role for some time while he regains command. Granted, that puts the Royals in a tough dilemma. Yes, Daniel Lynch IV has been good this year, but can he handle high-leverage outings consistently? This is the first year he's really been in those situations.

And the options are thin after Lynch.

While some are questioning Matt Quatraro for bringing in Erceg, his other options were to push John Schreiber to another inning (not a good idea), or call on Steven Cruz, Eric Cerantola, or Eli Morgan. Safe to say, the results would've probably been similar to Erceg with those other pitchers.

Which leads to a bigger question: why have the Royals struggled to build bullpens under JJ Picollo?

Granted, some of it has been injury luck, but the Royals have had a mediocre-to-bad bullpen under Picollo in 2.5 of his 4 seasons as President of Baseball Operations. While some organizations like the Cleveland Guardians and Seattle Mariners have become bullpen factories, the Royals have been the opposite. 

The Ercge and 2026 bullpen situations emphasize that some changes are needed. Whether it's making changes in coaching, talent acquisition, or player development, the Royals have to do something. They can't continue this trend of poor performance in relief.

If it does, for another season or two, the Royals may be looking at a new regime up top. Let's hope that Erceg's struggles can be a catalyst for change from Picollo and the Royals' front office.