Simplify the following text for a Grade 9 native English-speaking person.
Original: William Clay Matthews III ( born May 14 , 1986 in Northridge , California ) is an American Football outside linebacker for the Green Bay Packers of the National Football League ( NFL ) .
Simplified: William Clay Matthews III ( born May 14 , 1986 ) is an American football linebacker for the Green Bay Packers of the National Football League .