The speculation stems from the actor's two appearances in the Agents of S.H.I.E.L.D. trailer. It's clear that whatever character he's portraying has special abilities, namely super-strength and super-invulnerability. Entertainment Weekly notes that those are two of Luke Cage's qualities as well. Add that Richards is shown in one scene wearing yellow (-ish) pants, a possible nod to Power Man's 1970s yellow-and-blue outfit.
But that's not the only potential character Richards could be playing. Chris Radtke pointed out that, thanks to a clue from the Marvel bumper at the beginning of the Agents of S.H.I.E.L.D. promo, Richards could be Rage of the New Warriors, not Luke Cage. Of course, Richards may play someone else entirely, but these are the two most popular theories, with the former explaining why the role was initially characterized as "super top-secret."
If Richards is playing Cage, this wouldn't be the first time Marvel tried to integrate the character into one of its TV projects. The failed AKA Jessica Jones series was supposed to feature Cage and Carol Danvers as supporting characters. Writer Melissa Rosenberg opened up about Cage's inclusion back in 2011.
“It’s very tricky navigation there,” she said of using characters from the Marvel Universe. "There are a lot of boundaries on who you can and can’t use. I had Jessica Jones and Luke Cage and Carol Danvers [for the pilot script]. Basically, I wanted those three guys -- then I would have a series. Everyone else we can be digging into lesser-known characters or taking known characters and renaming them.”
Officially part of ABC’s fall lineup, S.H.I.E.L.D. centers on the global espionage and law-enforcement agency that’s helped to provide the connective tissue between the films of the Marvel Cinematic Universe. Joss Whedon directed the pilot, which he co-wrote with his brother Jed Whedon and Jed’s wife Maurissa Tancharoen. It stars Clark Gregg as fan-favorite Agent Coulson, Ming-Na as Agent Melina May, Elizabeth Henstridge as Agent Gemma Simmons, Iain De Caestecker as Agent Leo Fitz, Brett Dalton as Agent Grant Ward and Chloe Bennett as Skye.