Learning curve: Royals' LHP prospect Lamkin refining pitch in Arizona Fall League

GLENDALE, Ariz. -- One year ago at their Spring Training facility, the Royals gave Justin Lamkin, the 71st overall pick in the 2025 Draft, his first major development assignment: get another breaking ball.

“I didn't have a curveball in college,” the Texas A&M product said. “That was something I took into last offseason, and we had a pitch design group. So I was in that to add a fourth pitch to the arsenal, give a different look to righties at least so it's not just fastball-slider. But I just stuck with it and trusted in our coaches.”

Lamkin would have continued to work on the deuce all summer long, if not for a left shoulder injury that cut his regular season short after May 25. Now the 22-year-old left-hander's back in the Grand Canyon State in the Arizona Fall League to not only reestablish his health but pick up where he left off with that curve development.

Why the Royals' No. 8 prospect needs the slower breaker, compared to the slider, couldn’t have been clearer through his first two outings for the Surprise Saguaros. 

Making his first start in 4 1/2 months on Oct. 6, he allowed five runs (four earned) in three inning. Of his 53 pitches in that outing, only 13 were curves (25 percent), though both of his strikeouts came on the pitch. On Thursday, he upped that usage to 37 percent (23 pitches of 62 total), and the results followed. He allowed only one earned run on one hit and struck out three (including one on the curve) over four innings in a 17-8 win on the road at Glendale.

Lamkin has elicited 17 swings against the 78-81 mph curveball through his two starts in the desert, and batters have come up empty seven times for a whiff rate of 41.2 percent. Pretty good for a pitch that he picked up a year ago. 

As part of that offseason assignment, Royals pitching coaches and instructors gave the southpaw a few grips to work with in hopes something would stick. What did was one that hooks his middle finger onto the baseball’s horseshoe and adds a “baby spike” with his pointer finger. 

“I was trying to throw myself out in front of the ball,” Lamkin said.

The offering takes off about 2-3 mph off the trademark slider from his days with the Aggies and drops about 1 foot more (47 inches on average in Wednesday’s outing). It comes with minimal horizontal movement, even sometimes breaking toward the armside, and it adds another level of verticality to Lamkin’s arsenal when it’s on and used, as it was Wednesday.

“I think trying to get back to who I am as a pitcher would be more like north-south, especially to righties,” he said. “It's what I worked on in my side last week.”

Lamkin’s more developed arsenal is a key reason why he looked like a potential breakout prospect in the spring and early summer before getting hurt. He was pumping four-seamers around 93-95 mph, up from 91-93 in school, and with the way his breaking balls (both old and new) were looking, Royals director of player development Mitch Maier told MLB Pipeline. “I'm really excited because, wow, this is what it looks like.”

Lamkin opened his 2026 campaign at High-A Quad Cities, moved to Double-A Northwest Arkansas in mid-May, and after three Texas League starts, he was pulled from his May 25 outing before throwing an actual pitch. At the time, he had a 2.04 ERA with 53 strikeouts and 14 walks in 39⅔ innings between both stops in the middle Minors.

The shoulder issue, which the Royals said at the time wasn’t structural in nature, quickly became a learning moment.

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“I think [you have to] really stay on top of your stuff,” he said. “That was my first time really getting injured, so it kind of happened out of nowhere. It's not like I felt something earlier in the week. It was just on the spot like that before a start. So just like dialing in my routine and see if I can do a little bit extra here and there to get the body to where it needs to be.”

Much like the curveball last offseason, that shoulder work will become a priority in Lamkin’s second professional winter once he’s done in the Fall League. But he still has a ways to go with the Saguaros before then. Next up: building back his fastball velocity to pre-injury levels after  averaging just 92.4 mph on the heater Wednesday. Then again if the curveball can work as it’s done with increased usage, Lamkin boosts his chances of scratching out quality outings even when his fastball or slider aren’t at their typical levels -- the whole point of an expanded arsenal.

“I think coming back off of injury, I'm still a little bit out of sync with the arm,” Lamkin said. “Just trying to time up the body a little bit better. I didn't really feel like it was coming out that good today, but I was still able to compete and go four innings. So that was a good part about it.”