Joe Theismann -- Kevin Ware's Gonna Be Fine (I Would Know)

NFL legend Joe Theismann -- famous for suffering one of the gruesomest career-ending injuries in sports history -- is optimistic about the recovery of Louisville basketball player Kevin Ware ... telling TMZ, Kevin's young enough to make a full comeback.

Theismann says he saw 20-year-old Ware's injury on TV Sunday night when it happened ... Louisville was playing Duke and Ware jumped to block a 3-pointer ... but he landed wrong on his foot and snapped his right shinbone through his skin.

Theismann -- whose QB career came to an end in 1985 when Lawrence Taylor snapped his leg like a twig during "Monday Night Football" -- tells us, "I got sick to my stomach ... It brought back a lot of memories that weren't very pleasant for me."