Four tennis titans and a few of their fans will rally together for a worthy cause at the fourth annual Greenbrier Champions Tennis Classic on September 26 and 27 in White Sulphur Springs, West Virginia. Held at the Greenbrier hotel (whose underground bunker was the planned emergency shelter for the U.S. Congress during the Cold War), the three-match tournament will host the sport’s elder statesmen Pete Sampras, John McEnroe, Jim Courier, and James Blake as they hold court at the resort’s newly constructed tenn…