Twins Rule 5 Pick Eiberson Castellano Weirdly Fits Perfectly in this Bullpen

The Twins' bullpen is exciting this season, at least on paper. Before making a single addition, the corps ranks first in FanGraphs’s WAR projection for the 2025 season. Now, obviously, that comes with the caveat that the game is played on the field, not on a spreadsheet, and all that. But it is a sign of both the depth and the star power of this pen.

Enter Eiberson Castellano. The Twins picked Castellano in the Rule 5 Draft last week. He comes to Minnesota with some potential to be a starter (with a three-pitch mix), but the Twins will surely use him out of the bullpen for the time being. As a Rule 5 draftee, he needs to stay on the active roster or MLB injured list for the full season, so the 23-year-old with 40 innings above Single-A will probably be used in low-leverage as much as the Twins can manage.

The club has also commented that the newest Twin will be deployed as a multi-inning reliever. This role keeps him somewhat stretched out, which is vital for his development as a starter (assuming they have any hopes that he can continue to start after 2025). But having a long reliever will also help keep the rest of the guys fresh.

Let’s talk briefly about the rest of the guys.

Right now, the Twins have seven other relievers who appear to be locks in the bullpen picture for one reason or another: Jhoan Duran, Griffin Jax, Cole Sands, Brock Stewart, Jorge Alcala, Justin Topa, and Michael Tonkin. That’s not including arms like Louie Varland, Kody Funderburk, Brent Headrick, Ronny Henriquez (who is already out of options), or the inevitable breakout minor league signing, (Did you see they signed an old friend from the Jaime Garcia trade, Huascar Ynoa last week?) Even someone like Matt Canterino could play a role.

The first six names mentioned are reasonably potential setup guys, at minimum. You’d feel fine seeing any of those six in the seventh inning, and Durán and Jax are a couple of the top relievers in baseball. Tonkin is a rubber arm middle reliever. Of course, it would be nice if one of those seven was left-handed, but a good arm is a good arm.

So what do you add to that mix? Someone who can eat innings when the game isn’t on the line—several at a time. Tonkin can carry some of that load, but it would also be beneficial not to have to burn A-bullpen arms when the game is out of reach or a starter exits early.

Some may point to such failed bullpen setups as the 2021 Twins, during which the team tried to carry Randy Dobnak as a long reliever but couldn’t find enough work for him. That’s probably the most significant risk in carrying a completely unproven rookie and trying to hide him for six months. However, it’s likely easier to get by having the six guys the Twins have over the likes of 2021 Alex Colome and Hansel Robles. Beyond that, they were actively trying to find Dobnak work—given that he was also their sixth starter on the depth chart—whereas the team probably won’t shed a tear if Castellano goes a week without pitching.

Now, though, instead of sending Alcala or Sands to throw 50 pitches in relief, that can be Castellano’s job. None of the arms that you prefer in close games need to stretch out to just cover innings. Tonkin (and his propensity to suck up innings like a Hoover) helps, but having a dedicated guy you can run out there helps more in a bullpen with this much back-end talent than it would in some other bullpens.

Put another way, the Twins are better served with Castellano in their bullpen than they would be finding a veteran middle reliever or another setup man to add to the mix. Every inning that Castellano eats is an inning that doesn’t disqualify another pitcher from throwing tomorrow, and if he throws multiple innings, that might be multiple back-end arms preserved for another day.

Then you can add in the potential long-term benefit—the club has reportedly loved Castellano for a while, and he might have a real future in the organization if he can survive the season. But of course, that’s next year.

There are some obvious caveats. There are questions in the top six—Stewart and Topa’s health, Alcala’s struggles late in 2024, a lack of an extensive track record for Sands and Topa, rumors that Jax might move to the starting rotation, and Durán’s diminished fastball velocity. But show me an MLB team and I’ll show you a bullpen that gives fans a stomach ache for one reason or another. It would be great if someone, anyone, in this mix was a lefty as well. Castellano might also just not be good enough right now (or ever) to keep his ERA below 6.00. 

On the other hand, the Twins do have depth. There are arms in the organization that probably deserve a shot at being in the pen, and it’s not hard to imagine guys like Varland, Canterino, or even Connor Prielipp being arms the team would feel comfortable with from the seventh inning on, and some of those guys are lefties. And if Castellano doesn’t make the cut, so be it. I’m sure the Phillies would accept him back for the $50,000, and the Twins could pivot from there.

However, if there’s a bullpen that could benefit from a true long reliever, it’s the one that the Twins have constructed this season. And it doesn’t hurt to have a guy literally locked into that spot.