EXCLUSIVE: As Game of Thrones starts season seven Sunday on HBO, discussion might soon turn to who among the ever-thinning cast will have the best chance of following the series with movie stardom after the battle for the Seven Kingdoms is settled. Sean Bean already had a screen career to return to when his Ned Stark character was cut down, and Jason Momoa is headed for big things with Aquaman after his Khal Drogo character died. Who among the current cast has the best chance for screen success? An odds on favorite has to be Nikolaj-Coster Waldau, whose Jaime Lannister figures out his place as his sister/lover and new queen Cersei seizes the Iron Throne. Waldau gets his chance to show his macho wiles in Shot Caller, the Ric Roman Waugh-directed grounded thriller about a businessman who falls down the rabbit hole when a DUI crash puts him behind bars when his friend is killed. He learns quickly that the key to survival is to progressively rise to the top of the prison population food chain by any means necessary. Waldau as a tattooed prison “shot caller?” Can he pull it off? Watch the exclusive clip above, and for good measure, view the trailer for a film that will be released August 18. Waugh has done his research in seeking to make a grounded thriller that focuses on the effects of incarceration. Son of the stuntman Freddy Waugh, he went into the family business before making his directorial debut on Felon.  He embedded himself by becoming a volunteer parole agent in California before attempting the movie which investigated the effects of the penal system on inmates. Shot Caller is the logical progression, exploring what the fall out would be like for someone to return to society after serving a decade in the belly of the beast. Pic bows on DIRECTV on July 20 before its theatrical bow. Here’s the trailer: