Reilly will reteam with executive producer Adam McKay on the pilot, where he's set to play team owner Jerry Buss.

HBO's drama pilot about the 1980s Los Angeles Lakers is undergoing a casting change.

John C. Reilly has signed on to play late team owner Jerry Buss in the project, which is being executive produced and directed by Adam McKay. He replaces Michael Shannon, who was initially cast in the role and has exited due to creative differences, sources tell The Hollywood Reporter.

Reilly will join a cast that also includes Jason Clarke, who is set to play Lakers legend Jerry West, the team's general manager in the '80s.

The as-yet-untitled pilot will chronicle the professional and personal lives of the '80s Lakers, who built a dynasty and helped define their era, both on and off the court. It is based on Jeff Pearlman's book Showtime: Magic, Kareem, Riley and the 1980s Los Angeles Lakers Dynasty.

Reilly's Buss, who bought the Lakers, the NHL's Los Angeles Kings and the Forum in Inglewood in 1979, is a self-made millionaire whose success has only amplified his proclivity for risk. He redefines American sports, celebrity and wealth by transforming the Lakers into a dynasty, but his house of cards threatens to collapse on him and the people he loves most.

Reilly and McKay have worked together a number of times in the past, including on Talladega Nights, Step Brothers and Holmes & Watson.

The role would be Reilly's first as a series regular in primetime (he starred on Adult Swim's Check It Out! With Dr. Steve Brule from 2010-16). He is repped by WME, Peg Donegan and attorney Michael Gendler.

McKay is executive producing with partner Kevin Messick, writer Max Borenstein, co-writer of the story Jim Hecht, Jason Shuman, Scott Stephens and Rodney Barnes.

The project is part of an HBO development slate that also includes a Game of Thrones prequel that is expected to go to series. Corporate parent WarnerMedia has given HBO a mandate to increase originals, both for the on-air network and as the linchpin of the forthcoming streaming platform HBO Max.

Among the HBO series set to debut in the near future are adaptations of Watchmen (from Damon Lindelof) and His Dark Materials (a co-production with the BBC); Armando Iannucci's space comedy Avenue 5; J.J. Abrams' sci-fi drama Demimonde; Joss Whedon's Victorian superhero drama The Nevers; and Industry, from Lena Dunham.