What we have here is one of the oddest film adaptations of an admittedly odd motion picture, which itself was adapted from a quirky novel. So, we have to look at both the film and the series.
"Semi-Tough" the motion picture, was a 1977 sports based romantic comedy, adapted from novel by Dan Jenkins, about a couple of pro football players (Burt Reynolds as Shake and Kris Kristofferson as Billy Clyde) on a Miami team and their female roommate (Jill Clayburgh as Barbara Jean) who just happened to be the daughter of their team's owner.
That seems simple enough, but then the movie becomes about some pseudo-scientific self-help program called B. E. A. T., which parodied a somewhat popular seminar that was actually happening at the time of the film, called "est." This seminar was supposed to give you confidence and help you see that the things in your life that were stumbling blocks can be removed with the proper attitude and understanding. The fictional "B. E. A. T." seminar presented in the film paralleled the factual "est" and the film showed how these three people got themselves involved in that program and what happened because of it.
In the film, the seminar leader was played by Bert Convy, and may have been where Bert and Burt got to be friends, eventually leading to their collaboration on a couple of projects, later.
In the television adaptation, there were quite a few wholesale changes.
First, they moved the football team from Miami to New York, and the basic set up of the first half of the plot was the same, with the two players (David Hasselhoff in the Reynolds role and Bruce McGill in the Kristofferson role) having flirtations with their female roomie (Markie Post in the Clayburgh role) and she somehow put up with their antics.
The concept clearly wanted to be another version of ABC's previous hit comedy "Three's Company," only with two guys and a girl and with a sports based theme.
Where the movie had that focus on the self-help seminar and the machinations surrounding it, the TV show basically avoided all of that and stayed on the three way relationship of the roommates, which almost ends as the series begins, with Barbara Jane moving in, then moving out. They kept the romantic part of the story out, for the most part, and had the characters be platonic friends, with the same sorts of flirtations and occasional borderline situations that were being seen on "Three's Company."
New York plays a part because this is a sports town, and certainly in 1980, the two NFL football teams in the area were as successful as the one depicted in this series, that is to say, not successful at all, which may have contributed to why they chose to move the location of the team to NYC, as the Miami Dolphins were consistently making the playoffs through this era.
The idea was to depict how the game on the field wasn't the only game that guys play and how emotions when you're fooling around with love can hit you like a blind-side tackle, which justifies the name of the series. Even the toughest of tough guys is only semi, when it comes to real romance.
The elements that made "Three's Company" work were largely missing from this series, those being the perpetual titillation, the clever writing, the constant spying by an authoritarian figure (even though that could have been easily added with the fact that the owner's daughter was living with two players, and why wasn't Dad monitoring that circumstance a lot more closely)?
Most of all, there was no John Ritter with his incredible comic talents. No offense to Hasselhoff and McGill, who have both done some pretty good comedy work (though they both delved more into drama, or self-parody in the case of The 'Hoff), they just aren't in the same league as Ritter was, and that missing part made for a losing season for the series.
