Simplify the following text for a Grade 9 native English-speaking person.
Original: Richard Marvin `` Dick '' Butkus ( born December 9 , 1942 ) is a former American football player , commonly considered as the greatest linebacker of his time and one of the best football players ever .
Simplified: Richard Marvin `` Dick '' Butkus ( born December 9 , 1942 ) is a former American football player for the Chicago Bears .