The Adjustment That Is Changing Nate Pearson in Kansas City

[Yirsandy Rodríguez]

Image courtesy of William Purnell-Imagn Images

Nate Pearson is 30 years old and is in his sixth season in the major leagues. He has pitched for four teams, has an 11-7 record and a 4.66 ERA with -0.2 bWAR in his career — the fWAR has handled his efforts better, placing him at a clean zero. In 2024, the Blue Jays trusted his right arm and gave him enough work to stabilize himself. He never did. He relieved in 41 games and finished with -0.6 bWAR, a 74 ERA+, and a 4.64 FIP. His strikeout rate seemed interesting (11.5 K/9), but he received cruel punishment from the opposition with a 1.8 HR/9 rate. Then, the Cubs tried to fix his inconsistencies. They couldn't either. The 83 ERA+ that Pearson recorded during four seasons in Toronto dropped one more step, finishing at 80.

The Houston Astros gave him another opportunity, and his performance improved considerably, but he could not remain part of the plan. That was how Pearson arrived in Kansas City at the end of July, where he found the worst bullpen in the Major Leagues this year. The Royals' relievers have the worst fWAR (-3.2) and the worst xERA (4.86) in all of the Majors, along with the worst xFIP (4.82) in the American League. Even so, for Pearson, the news did not seem so devastating. He had a new job. Since then, his performances have been surprising, to the point of placing himself as one of the team's most consistent relievers. In his first 15 appearances with the Royals since last July 26, Pearson leads the bullpen with a 0.61 ERA, .189 BABIP allowed, a high 93.8 LOB%, and has not allowed home runs against 59 opponents. His 0.2 fWAR is only behind Daniel Lynch IV (0.3).

In four of his first five appearances, the Royals used Pearson in games with the score against them. The first time they handed him the ball to relieve in a key situation, he could not do an effective job against the Minnesota Twins on August 6. He inherited runners on first and third after one out, with a one-run lead during the top of the eighth inning. Pearson ended up allowing both runs. In his next appearance, he managed to close out the game in the 6-3 win against the Chicago Cubs.

Since then, he has appeared six times in the eighth and four in the ninth, delivering very effective relief appearances. His only failure was on August 15, when he allowed one run in the bottom of the eighth against the Angels, who eventually took the 1-0 victory. From being a reliever in already-lost games, Pearson's consistency has changed how the Royals plan his role. He has recorded four holds, a pair of saves and a 0.51 ERA in his last 18 relief appearances, including his last outings with the Astros. If we go a little farther back, Pearson has allowed only two earned runs or fewer on two occasions during his last 26 outings.

The Astros have had one of the strongest bullpens throughout the entire season, so it was difficult to keep a spot for Pearson. However, after his arrival in Kansas City, he has taken advantage of the opportunities, and his adjustments are still underway. The big question here, of course, is how he is doing it. Compared to his arsenal from last year, Pearson has made two key adjustments: first, he brought back the sinker, which we will talk about in a minute. And along with the mix of the fastball and slider, he is also giving the curveball more use. In a smaller proportion, he has brought back the changeup for the first time since 2021, but only in very specific situations against left-handed hitters.

That said, there is a really interesting story around his sinker, as it is becoming an important weapon: it has 4.4 inches less vertical movement than his four-seam fastball (16.5" IVB at 97.7 mph). He does not use it as often, nor is it his main swing-and-miss pitch — the four-seamer and slider remain his main options — but hitters have an offensive line of only .067/.222/.067 against the sinker.

Year	Pitch	Avg. Miss Dist. (Inches)	Flawed Swing %	Perfect Contact %	Over	Avg. Over Dist. (Inches)	Lined Up	Under	Avg. Under Dist. (Inches)
2025	Curveball	--	20%	0%	40%	-3.8	60%	0%	--
2026	Curveball	4.1	16%	16%	42%	-4.6	53%	5%	2.3
2026	Changeup	0.2	0%	17%	0%	--	67%	33%	3.0
2023	Four Seamer	0.7	2%	19%	2%	-2.2	46%	52%	3.0
2026	Sinker	2.0	0%	19%	11%	-3.4	73%	16%	2.8
2023	Curveball	--	0%	20%	0%	--	100%	0%	--
2024	Slider	5.0	13%	20%	29%	-4.5	62%	9%	3.0
2026	Slider	3.8	7%	20%	25%	-3.9	63%	12%	2.7
2024	Curveball	7.0	16%	23%	32%	-6.5	68%	0%	--
2025	Slider	4.6	8%	24%	14%	-5.5	68%	18%	2.7
2026	Four Seamer	1.2	3%	24%	1%	-4.8	59%	41%	3.2
2023	Slider	5.7	8%	31%	8%	-7.7	54%	38%	2.5
2024	Four Seamer	1.2	3%	31%	<1%	-2.6	60%	39%	3.1
2025	Four Seamer	1.1	3%	40%	3%	-2.5	74%	24%	3.0
2024	Sinker	0.1	0%	43%	0%	--	93%	7%	2.0

Look at a determining detail here: hitters have reduced their Perfect Contact% from 50% last year to 19% this season. The most concerning point could be how hitters continue to register a high Lined Up percentage (73%) against the sinker. That point connects quite a bit with the fact that Pearson's sinker whiff rate is the lowest of all his pitches, only 10.5%. However, the average exit velocity is at 82.6 mph, and this has a lot to do with the improvements in the sinker's Vertical Drop, which has reached 16.9.

While the sinker begins to take more prominence in his repertoire, the curveball and slider continue to record the highest rates of swings and misses, at a time when Pearson's fastball is above his average velocity this season.

Although there is still a lot to see about how all these adjustments evolve, Pearson had never had a month with this much dominance in his entire career. That moment has arrived as he begins to resurface as an interesting piece in the worst bullpen in the majors this season. We will see what comes next. But for now, Pearson is taking advantage of this opportunity.

 

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