Sloane Stephens will be playing with the Kastles on July 22 . (Photo by Matthew Stockman/Getty Images)

The Washington Kastles are adding more star power.

Sloane Stephens, the second-ranked American woman behind world No. 1 Serena Williams, is joining a lineup that already includes seven-time Grand Slam champion Venus Williams and former top-ranked major champion, Martina Hingis, the team announced Wednesday.

“Sloane Stephens is the most captivating shot-maker and sizzling court-mover to come along since Serena,” Coach Murphy Jensen said in a news release.

Stephens, 21, will play in Washington when the three-time defending champion Kastles take on the Springfield Lasers at George Washington University’s Smith Center on July 22.

“I’ve followed the Washington Kastles’ success ever since I first played Mylan World TeamTennis, and it feels great to finally call myself a Kastle,” said Stephens, who is currently ranked No. 19 in the world. “I can’t wait to be part of another championship run in Washington.”

Stephens, who will play Slovenia’s Polona Hercog in the second round of the French Open, announced her arrival as a Grand Slam contender when she beat Serena Williams in the quarterfinals of the 2013 Australian Open. She also reached the quarterfinals of last year’s Wimbledon, losing to the eventual champion, Marion Bartoli of France.

Also joining the team is South Africa’s Kevin Anderson, the world No. 20 who will play unseeded Frenchman Axel Michon in the second round at Roland Garros.