Minnesota Twins Prospect Retrospective: John Klein

Not every prospect arrives with hype, signing bonuses, or a clear path to the majors. Some take the scenic route, winding through back fields, small schools, and relative anonymity before forcing their way into the conversation. John Klein fits that description perfectly. After a breakout 2025 season, he is no longer flying under the radar.

A Minnesota native from Brooklyn Park, Klein’s baseball journey started without much fanfare. He went undrafted out of Iowa Central Community College in 2022, eventually signing with the Twins as a free agent after showing promise in the Northwoods League. At the time, he looked like organizational depth: a tall right-hander with projection, but limited present stuff. What has happened since then is a steady and impressive climb.

Klein spent the next two seasons quietly working his way through A ball, refining his mechanics and building strength. In 2023, he moved from Rookie ball to High-A. He posted a 4.17 ERA, with a 23.9 K% and a 9.0 BB% across 58 1/3 innings. Minnesota had him return to Cedar Rapids for the entire 2024 season. In 100 1/3 innings, he posted a 4.57 ERA with a 20.4 K% and an 8.6 BB%. He wasn’t overpowering or putting himself on the prospect radar.

That changed in 2025, when everything started to click. Pitching for Double-A Wichita, Klein posted a 3.12 ERA with 95 strikeouts across 80 2/3 innings, establishing himself as a legitimate arm in the system. A late-season promotion to Triple-A brought mixed results, but he still managed 33 strikeouts in 25 2/3 innings against more advanced competition.

The transformation is not just statistical. At 6-foot-5 and now around 225 pounds, Klein has added noticeable strength to his frame. Early in his pro career, he sat around 90 mph with his fastball. By 2025, that number had climbed into the mid-90s, averaging 94 and touching 97. The Twins’ development system deserves credit here—particularly their velocity programs, which have unlocked more from previously modest arms. Klein’s delivery adds deception, allowing the fastball to play up even further.

His arsenal has grown alongside the velocity. What once was a limited mix has evolved into five distinct pitches. The biggest development has been his curveball, now sitting around 80 mph with sharper break and the potential to miss bats when located well. He's also worked in a splitter in the mid-80s and an upper-80s cutter, giving him multiple looks against hitters from both sides of the plate.

That said, there are still questions about his long-term role. While Klein has the repertoire of a starter, he doesn't yet possess a consistent put-away pitch. The curveball flashes that potential, but can be inconsistent, and without a true swing-and-miss offering, he may struggle to turn lineups over multiple times at the highest level. Some within the organization believe his stuff could tick up even more in a bullpen role, where shorter outings might allow everything to play at peak intensity.

Even with that uncertainty, Klein has already forced his way into the Twins’ plans at the highest level. After being added to the 40-man roster this offseason, he didn't have to wait long for his opportunity, making his big-league debut on Saturday. The early look confirmed what the organization has believed for a while now: that his development has put him in a position to contribute in a meaningful way.

There's something fitting about Klein’s trajectory. A local kid who grew up a short drive from Target Field now is pitching there, not as a highly touted draft pick, but as a player who earned every step along the way. Whether he settles into a rotation spot, a swingman role, or a multi-inning relief job, Klein has already exceeded expectations and reshaped his outlook.

For an organization constantly searching for pitching depth, stories like this matter. And for Klein, the next chapter could be the most meaningful yet.

Interested in learning more about the Minnesota Twins' top prospects? Check out our comprehensive top prospects list that includes up-to-date stats, articles and videos about every prospect, scouting reports, and more!