Hagans returned to his alma mater, Virginia, after his NFL career and stayed there for 11 years.
O'Brien will return to the position he held prior to filling the Penn State head coaching vacancy in 2012.
Many Nittany Lions made their mark on the NFL's Divisional Round.
After three seasons spent with the Minnesota Vikings, Chisena will head back to his home state to play for the Steelers.
Kency is the third running back to join the Nittany Lions' Class of 2023.
Virginia's Marques Hagans spent the last decade coaching at his alma mater.