Todd Christensen Dead at 57 -- NFL Legend Dies During Surgery

Oakland Raiders tight end Todd Christensen -- a 5-time Pro Bowler who went on to host "American Gladiators" -- died this morning during a surgical procedure in Utah. He was 57.

It's unclear what Todd was being treated for ... but he had battled liver disease and other illnesses in recent years.

Todd had a stellar 10-year career in the NFL -- and went on to co-host the 1st season of "American Gladiators" in 1989.

After that, Todd became an NFL broadcaster -- and worked with the "NFL on NBC" from 1990 to 1994.

Story developing ...