Watch the Trailer for HBO Mockumentary '7 Days in Hell'

HBO Sports is best known for its documentaries and boxing match offerings, but the company is doing something a little different with 7 Days in Hell: it's a mockumentary about an epic tennis match between two intense rivals, played by Andy Samberg and Game of Thrones star Kit Harington. And like a good mockumentary, this one seems to mine some great comedy from its authenticity.

7 Days in Hell looks like it could be an actual documentary about actual tennis players, if not for Samberg's hair, which is just a little too absurd to be legit. But the '80s and early '90s were a thing, so it's slightly believable. Here's the official synopsis from HBO:

This sports 'documentary' brings together Andy Samberg and Kit Harington for a look back at a pair of fictional players from the not-too-distant past, who played the longest and greatest tennis match of all time: a seven-day, five-set marathon that took literally everything out of them. In addition to highlights (and lowlights) from the match, the special looks back at the lives and careers of the competitors: Aaron Williams (Samberg), a hyper-malcontent, and Charles Poole (Harington), a dim-witted prodigy who carried England’s hopes for a tennis champion on his shoulders.

7 Days in Hell premiered at the SXSW film festival back in March, where it received mostly positive reactions. The film is about an hour long, which is perfect HBO Sports doc-length, and it features a great supporting cast of very, very funny people: Will Forte, Fred Armisen, Michael Sheen, Lena Dunham, Karen Gillan, Mary Steenburgen, tennis pro John McEnroe and June Squibb.

7 Days in Hell premieres on HBO on Saturday, July 11.