Now the name may seem familiar and yes, Will Decker would go on to appear in Star Trek: The Motion Picture in 1979. Decker would be played by now-disgraced actor Stephen Collins, most famous for his time with the WB/CW show 7th Heaven, and his 2014 outing of being a very bad guy.
Even though Decker was cast for the film, when the production of Phase II had shut down, the series had yet to find Decker’s actor. It’s unclear if Collins was ever considered or approached for the character on the television show, or who else was actually being looked at.
According to various outlets, Decker’s Phase II character would find a second life in the form of Star Trek: The Next Generation’s Will Riker. While the character wasn’t necessarily retooled, some of the same elements of the Decker character were found in the Riker character.
Decker was seen in the story as being the guy in training, maybe capable of replacing Kirk as captain one day, but for now, was a man who was duty-bound. A serious man, Decker would serve as Kirk’s first officer and would be focused on making sure the ship was stocked with the best personnel possible.
The idea of him seems to be a perfectionist, though one who can joke and laugh about.
He’s the only character who was never cast in the show but ended up in the film.