Every year, one undrafted free agent makes you pause and think, How did he not get picked?
For me, in 2025, that player is Pittsburgh Steelers defensive back Sebastian Castro.
The Steelers quietly signed the former Iowa standout following the draft. I believe this may be one of the smartest moves of the offseason. Castro wasn’t just another name in the Big Ten—he was a third-team All-Big Ten selection in 2024, racking up 39 tackles and three tackles for loss across 12 games.
He plays with aggression, downhill urgency, and a tenacity that screams “Steel Curtain.”
This signing came on the heels of a draft in which the Steelers doubled down on physicality. They used premium picks on tone-setting defenders, reinforcing their trademark identity of smashmouth football. Adding Castro to that mix feels like a continuation of that philosophy—gritty, relentless, and violent at the point of attack.
What I love about Castro is his versatility. He has experience as an outside linebacker from 2022 and made a seamless transition to the secondary, showing that he can play close to the line, fight through traffic, and still cover in space.
Pittsburgh Steelers found a gem in undrafted free agent Sebastian Castro
That hybrid profile fits perfectly into the modern NFL, and more importantly, it fits what Pittsburgh likes to do with its sub-packages.
I don’t expect Castro to walk in and start—few undrafted rookies do—but I see a path for him to make the roster and contribute as a nickelback or special teamer. He’s a player who will thrive in training camp when the pads come on.
If he can stick through those grueling weeks, don’t be surprised to see No. 29 flying around in preseason making plays.
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Pittsburgh has a history of developing hard-nosed defenders with chips on their shoulders—guys like James Harrison come to mind. Castro might not be a household name yet, but the traits are there: production, physicality, and most importantly, hunger.
I’m rooting hard for Sebastian Castro. Not just because he deserves a shot, but because I genuinely believe in his long-term impact. The Steelers might have found more than just a camp body—they might’ve landed their next defensive difference-maker.