Simplify the following text for a Grade 9 native English-speaking person.
Original: Robert John Riggins , nicknamed `` The Diesel '' , ( born August 4 , 1949 ) is a former American football running back in the National Football League for the New York Jets and Washington Redskins .
Simplified: Robert John Riggins ( born August 4 , 1949 in Seneca , Kansas ) is a retired American football quarterback who used to play for the New York Jets and Washington Redskins of the NFL . He was nicknamed `` The Diesel '' .