Venus Williams played for the Kastles last July against Kansas City. This year, both she and her sister Serena are expected to make an appearance for the World Team Tennis franchise. (Matt McClain/FOR THE WASHINGTON POST)

Venus and Serena Williams will return to Washington this summer to lead the Washington Kastles’ defense of their 2011 World Team Tennis championship.

Kastles owner Mark Ein ensured the sisters’ return by protecting both star players on the eve of the league’s marquee draft, held Tuesday in New York.

“Obviously we’re thrilled to have them back, and with a perfect title season to defend, we certainly need all the help we can get,” Ein said. “People will be gunning for us, and having them on the team is terrific.”

The 2011 Kastles compiled the first unblemished record in WTT history (16-0). In addition to the Williams sisters, they will return Coach Murphy Jensen and are expected to bring back the core of the team for a second season at the waterfront venue in Southwest Washington.

Earlier this month, Venus Williams played her first competitive match since withdrawing from the 2011 U.S. Open following her diagnosis of Sjogren’s Syndrome, an autoimmune disorder that often causes fatigue. Williams emerged from a near six-month hiatus for a Fed Cup tie against Belarus, teaming with the world’s top-ranked doubles player, Liezel Huber, for a 6-1, 6-2 victory that delivered a 5-0 sweep for the Americans.

By taking part in Fed Cup, Venus, 31, fulfilled one key requirement for earning a spot on the 2012 U.S. Olympic team. Under International Olympic Committee rules, she still must raise her world ranking in order to qualify for the London Games, where tennis will be contested at the All England Club, site of her five Wimbledon championships. Currently ranked 137th in singles, Venus has until early June (through the French Open) to climb into the top 60-68 in the world — the range of the IOC’s cutoff for Olympic berths.

To that end, Venus recently entered the Family Circle Cup in Charleston, S.C. (March 31-April 8) and is expected to compete in the hard-court tournament in Miami that precedes it. Venus won the gold medal in singles at the 2000 Sydney Games and teamed with sister Serena to win the gold in doubles that year and at the 2008 Beijing Games.

The 2012 WTT season will run July 9-28.