If Anthony Davis and Marcus Teague and Michael-Kidd Gilchrist were to decide not to accept scholarships from the University of Kentucky but instead to rent out a basketball arena and charge the public money in exchange for displaying their basketball skills, they are free to do that.
The notion that there should be some sort of legal remedy on behalf of these basketball-playing individuals that should override the terms and conditions offered by the universities to persons considering accepting scholarships from them has no basis in any claim of "monopoly" power.
The market, properly defined, is the entire market for the display of basketball skills. There is a whole world of opportunities for someone to obtain compensation for their basketball-playing abilities beyond the NCAA and beyond the NBA. Nothing prevents any group of basketball players from forming their own league and charging admission, for example.
The reality is that what we would see if Davis and Teague and Gilchrist did that is little interest on the part of the public. In fact, they simply don't in fact bring to the table as much as what people who claim they are being unfairly oppressed by monopoly power argue they bring to the table, and that would be readily apparent if they went out into the market and offered their basketball services directly.
One could argue that the universities should not be allowed to collude on the terms and conditions of athletic scholarships through the mechanism of the NCAA (or otherwise), but that is a different argument entirely than the claim of abuse of monopoly power.