Hornung, though, sued only Riddell, so that his case would not be lumped together with the class-action suit, which is being heard in Philadelphia.

In his complaint, filed in state court in Illinois, Hornung claims that Riddell should have warned players that its plastic helmets, while helping to prevent skull fractures, “provided no protection” against brain trauma, including concussions.

“Prior to, during and after Paul Hornung’s N.F.L. football career, Riddell knew of the harmful long-term effects of brain traumas sustained by football players while wearing Riddell’s supposed protective equipment; however, it misrepresented and concealed these facts from Paul Hornung,” the complaint said.

Erin Griffin, a spokeswoman for the company, said that Riddell was not aware of Hornung’s lawsuit and that it did not comment on continuing litigation.