EXCLUSIVE: Colin Donnell (Arrow, The Affair) has been added to the cast of NBC’s new drama series Chicago Med as a new regular. Because the latest offshoot in Dick Wolf’s Chicago franchise started off as a planted spinoff episode of Chicago Fire, the cast was not fully formed and is now expanding. Since work on the show’s 13-episode order is just beginning, the character Donnell will be playing is still being fleshed out. He is expected to be a doctor, possibly in pediatrics.

Donnell had been on NBC and Wolf’s radar for a while. Wolf previously liked him for a role on the first Chicago Fire spinoff, Chicago PD. This past season, NBC cast him in a guest-starring role on freshman drama Mysteries Of Laura and as a lead in drama pilot Love Is A Four Letter Word.

Chicago Med is described as an emotional thrill ride through the day-to-day chaos of the city’s most explosive hospital and the courageous team of doctors who hold it together. Donnell joins original series regulars Oliver Platt, S. Epatha Merkerson, Laurie Holden, Nick Gehlfuss and Yaya Dacosta.

Donnell, repped by Gersh, played Tommy Merlyn on CW’s Arrow and has a recurring role on the Showtime drama The Affair.