Serena Williams and Maria Sharapova signed up to play in the World TeamTennis Pro League in July.
Williams, an eight-time Grand Slam champion, will join the St. Louis Aces when they host the New York Sportimes on July 23.
Sharapova, winner of two majors and currently ranked No. 2, will play for the Newport Beach Breakers when they host the Kansas City Explorers on July 26.
Other players who have agreed to play in the July 5-25 regular season include Williams' sister Venus, Pete Sampras, John McEnroe and Anna Kournikova