John McMillon signed as an undrafted free agent with the Royals after the shortened 2020 MLB Draft. His rise through the system since then took some time, but once he took off, McMillon flew through the minor leagues. It’s difficult to state just how dominant McMillon was throughout the 2023 MLB season. He compiled 91 strikeouts in just 51.1 minor league innings last summer. His 45.3% strikeout rate was the best in the entire system…by more than 13%. McMillon finished the year with an insane 32.8% K-BB% (again, best in the organization) and a 1.85 FIP (you guessed it, the best in the organization).

Season Stats:

2022 (Low-A): 26 G, 31.0 IP, 6.10 ERA, 5.56 FIP, 30.8% K%, 26.0% BB%

2023 (Low-A): 9 G, 10.2 IP, 3.38 ERA, 1.45 FIP, 48.8% K%, 14.0% BB%

2023 (High-A): 13 G, 20.0 IP, 2.70 ERA, 1.51 FIP, 51.9% K%, 10.4% BB%

2023 (AA): 15 G, 20.2 IP, 0.87 ERA, 2.39 FIP, 37.0% K%, 13.6% BB%

2023 (MLB): 4 G, 4.0 IP, 2.25 ERA, 2.51 FIP, 61.5% K%, 0.0% BB%

Although McMillon wowed fans by moving through the entire farm system in just one season, the more impressive feat might be how consistently dominant he was at every stop. All of that success culminated in a short major league debut that only ended prematurely due to injury. McMillon suffered a forearm strain after just four MLB appearances and would go on to miss the remainder of the 2023 season. Command held him back early on in his professional career, but it was immensely improved last season.

It’s a two-pitch mix for McMillon, who relies heavily on a fastball and a slider. Both pitches are elite. His fastball touches triple digits with ease and the slider lands in the upper-80s with good breaking action. McMillon pairs his elite arsenal with a bulldog mentality on the mound. He’s a fierce competitor and has the mindset to become one of the best late-inning relievers in the league. That relies heavily on him maintaining his newfound command.

Scouting Grades:

Fastball: 65/70

Slider: 65/65

Command: 40/50

Best Case Scenario

McMillon showed last season just how good he can be. Then, even if it was an extremely short four-game sample, he continued that success into the big leagues. There’s true late-inning potential here and a path forward that could see McMillon become one of the best closers in the league. A more likely scenario probably sees him become somewhat close to Tommy Kahnle — a reliever with a live arm, excellent strikeout ability, and inconsistent command that bites him at times. A solid list of outstanding relievers have come out of Kansas City in recent years and McMillon looks like the next on the list.

Worst Case Scenario

You don’t have to look far to find a similar pitcher to McMillon with worse results. Christian Chamberlain offers a 60-grade fastball and 60-grade curveball but the command hasn’t come through quite yet. Chamberlain struck out 28% of hitters last season but walked 22.4%. Command looked substantially improved for McMillon last season, but it could regress to what we have seen in prior years as well. If McMillon struggles to find consistent command, he should still offer value as a reliever, but more akin to a mid-relief option, somewhere around 2022 Josh Staumont.