EXCLUSIVE: The Shield and Saving Grace alum Kenny Johnson is joining another cop drama with an iconoclastic detective at its center. Johnson has been cast as a regular on the upcoming NBC series Prime Suspect, an adaptation of the popular British drama starring Helen Mirren. NBC’s Prime Suspect stars Maria Bello as Jane Timoney, a female detective struggling to make her bones in a tough New York precinct dominated by men. Johnson will play Matt Webb, her boyfriend. The role has been recast and tweaked after the pilot where the character was played by Toby Stephens. Peter Berg directed the pilot for NBC’s Prime Suspect from a script by Alexandra Cunningham. The series, which co-stars Aidan Quinn, will premiere on September 22 and will air in the Thursday 10 PM slot. Johnson, repped by Paradigm and KLWG’s Eric Kritzer, recently recurred on FX’s Sons of Anarchy.