Forrest Griffin -- one of the most popular fighters in the UFC -- is backing out of his fight later this month because of a bum shoulder ... TMZ has learned.
Sources tell us the former UFC light heavyweight champ's shoulder injury is serious enough that he won't be able to fight Lil' Nog on May 29 in Las Vegas.
The extent of Griffin's injury is unclear.
UFC Star's Cold Shoulder Stops Fight
5/3/2010 7:30 PM PDT BY TMZ STAFF
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