Simplify the following text for a Grade 11 native English-speaking person.
Original: Diego J. Sanchez ( born December 31 , 1981 ) is an American mixed martial artist ( MMA ) with a background in wrestling and Gaidojutsu , system of submission wrestling developed by his longtime trainer Greg Jackson .
Simplified: Diego `` The Nightmare '' Sanchez ( born December 31 , 1981 in Albuquerque , New Mexico ) is a Mexican American mixed martial artist ( MMA ) . He has a background in wrestling and Gaidojutsu , a system of submission wrestling developed by his longtime trainer Greg Jackson .