Serena Williams takes step necessary to return to professional tennis by reentering international anti-doping testing pool

By Jill Martin, CNN (CNN) — More than three years since playing her last match, 23-time grand slam singles champion Serena Williams recently has taken a step that would be necessary should she want to return to professional tennis. Williams, 44, appears on a list on the International Tennis Integrity Agency’s (ITIA) website showing players