Jacob Allen O'Brien is a retired American professional mixed martial artist who most recently competed in the Heavyweight division. A professional competitor from 2005 until 2012, he fought for the UFC, WEC, and DREAM.
Biography：Jacob Allen O'Brien is a retired American professional mixed martial artist who most recently competed in the Heavyweight division. A professional competitor from 2005 until 2012, he fought for the UFC, WEC, and DREAM.
