Steelers' undrafted rookie could be a hidden gem

The Pittsburgh Steelers should be happy with their selections in the 2025 NFL Draft. Pittsburgh was able to address multiple positional needs, but mainly the defensive line. The Steelers drafted two interior defensive linemen and an edge rusher in Derrick Harmon, Yahya Black and Jack Sawyer. Offensively, the Steelers also added depth to the running back room by selecting Kaleb Johnson. Heading into the draft, quarterback was probably the Steelers' biggest need as they currently only have two on the roster, of which neither is considered a long-term option. The addition of Will Howard will help round out the quarterback room.

Each player who heard his name called during the draft made a dream come true. However, the opportunity to join an NFL roster for a rookie doesn't end when the draft is over. There are plenty of players still looking for an opportunity to show they can play at the next level. 

Undrafted free agent Sebastian Castro, a safety who played for the Iowa Hawkeyes, will be looking to prove that this summer during the Steelers' training camp. Dane Brugler, NFL Draft analyst for The Athletic, wrote about how some of the best undrafted free agents of the 2025 NFL Draft can help a franchise. 

"As soon as the 2025 NFL Draft concluded, teams began signing undrafted free agents (UDFAs)," Brugler wrote. Those players help fill out summer rosters for minicamps and training camps, but there usually are a few diamonds in the rough who can develop into impact players — Beanie Bishop Jr., Ivan Pace Jr., Brandon Aubrey, and Rashid Shaheed are all UDFA success stories from recent classes."

Castro was one of the undrafted free agents to make Brugler's list. Castro has a lot of upside to his game and could help as a backup safety in year one. With Juan Thornhill and DeShon Elliot both under contract for the 2025 season could open up opportunities for Castro to prove himself throughout the year and establish consistent snaps per game. 

Castro has the upside to be a diamond in the rough of this undrafted free agent class. His style of play also fits the mold of what coach Mike Tomlin is looking for in terms of physicality. Castro plays the game fast and physical, which is what the Steelers want in a player. Castro is constantly looking to deliver a big hit, whether it's to a wide receiver coming across the middle or meeting a running back in the gap. 

Castro is best when playing downhill and could provide help in the second line of defense in the run game. Brugler's analysis of Castro is that he would be a good backup safety in nickel schemes.

"Castro is an instinctive zone defender with trustworthy football character, but his ordinary speed and explosiveness limit his upside in most schemes," Brugler wrote. "He fits best as a big nickel safety, likely as a backup."

Castro is not the fastest player, but he has quick instincts that help him recognize route developments when playing in zone. However, due to the lack of speed, Castro may have a difficult time in man coverage in the NFL.

The Steelers would love to find a hidden gem 

With Thornhill and Elliott on expiring contracts, the Steelers would be excited if Castro developed into a rotational player. The Steelers probably won't be able to bring back both Thornhill and Elliot in 2026. Therefore, it would be in the Steelers' favor if Castro were a diamond in the rough and could produce similar results as either Thornhill or Elliot. 

Castro could be that diamond in the rough for the Steelers, especially with the awareness and physicality he plays with. The NFL game is fast, but there are other ways to win a matchup as a defensive back, even when you are outmatched in speed. 

Do you believe Castro will be a diamond in the rough for the Steelers this year?