The Latest on the U.S. Open (all times local):

12:30 p.m.

The U.S. Tennis Association announced a multi-year partnership with Adidas on Thursday to make the German sportswear giant the official sponsor of USTA player development.

Financial terms were not disclosed for the deal, which gives Adidas a presence throughout the USTA National Campus in Orlando, Fla. — the headquarters of the organization's player development efforts — and branding of the USTA's top-flight junior tournament series and league tennis.

USTA Player Development general manager Martin Blackman says the partnership also makes Adidas the official outfitter of player development coaches "to reflect the look and professionalism that exemplifies Team USA."

Adidas is the sponsor of such stars as Ana Ivanovic and Angelique Kerber. The company's U.S. senior director of tennis David Malinkowski noted that the partnership could also help forge relationships with up-and-coming American tennis stars.

11 a.m.

Venus and Serena Williams are set to play back-to-back, second-round matches Thursday in Arthur Ashe Stadium, which may need its new retractable roof for much of the day because light rain is falling and more is expected.

No. 6-seeded Venus Williams will take on Julia Goerges of Germany in the afternoon, followed by No. 1 Serena Williams against Vania King in an all-American matchup to start the night session.

Another key match comes in the nightcap on Ashe, when 2009 champion Juan Martin del Potro takes on 19th-seeded American Steve Johnson. Del Potro, whose ranking dropped to No. 142 because of wrist injuries over the past 2 ½ years, has returned to Grand Slam play this year and made a strong run to the silver medal at the Olympics.

The Wimbledon champ and Olympic gold medalist, No. 2-seeded Andy Murray, is also in action on Ashe, facing Marcel Granollers. They've played seven previous times, with Murray winning six.