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

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.

​ 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. Read More Breaking News, Latest News and Videos | CNN