Hardy was drafted No. 219 overall in the 2024 NFL Draft.
Clifford was Penn State's leader in wins as a starting quarterback, passing yards, total yards, and passing touchdowns.
Castro-Fields appeared in eight games for the Commanders last season.
For the second straight season, there's a battle for Penn State's starting placekicker spot.
Prior to the 2024 season, James Franklin announced Cooper Cousins and Dejuan Lane will burn their redshirt this season.
The secondary lost four experienced starters at the end of the 2023 season.