Simplify the following text for a Grade 6 native English-speaking person.
Original: David Allan Aardsma ( Ë É ` rdzmÉ ; born December 27 , 1981 ) is an American Major League Baseball relief pitcher for the Seattle Mariners .
Simplified: David Allen Aardsma is an Major League Baseball pitcher . He plays for the Seattle Mariners and is the team 's closer .