2012 CitiOpen winner Alexandr Dolgopolov will be back to defend his Washington title. (Nick Wass/AP)

One month before Washington’s Citi Open gets under way, the 48-player field for the hard-court classic is taking shape, headlined by No. 7 Jo-Wilfried Tsonga and four past champions, including fan favorite James Blake, who claimed the 2002 title.

In the 32-player women’s tournament, which will also be contested at the William H.G. Fitzgerald Tennis Center in Rock Creek Park. No. 16 Nadia Petrova will likely be the top seed. She’ll contend with a promising group of young Americans, including Sloane Stephens, Madison Keys and Christina McHale.

The men’s draw, back to full strength following last summer’s scheduling conflict with the London Olympics, includes the entire U.S. Davis Cup squad—19th ranked Sam Querrey, John Isner (No. 21) and the top-ranked doubles team of Bob and Mike Bryan, who recently claimed their 90th career victory at London’s Queen’s Club. The 35-year-old Bryan brothers have won 14 Grand Slam championships, claimed the gold medal in doubles at the 2012 London Olympics and are three-time victors in Washington.

In all, 17 of the world’s top 50 men’s players will be in town. Among them: Kei Nishikori of Japan (No. 11); Tommy Haas (No. 13) and American Mardy Fish (No. 43). Also returning are defending champion Alexandr Dolgopolov; past champions Radek Stepanek (2011) and Lleyton Hewitt (2004); and previous finalists Gael Monfils and Marcos Baghdatis.

Rising young players Bernard Tomic of Australia, Grigor Dimitrov of Bulgaria and American Ryan Harrison are also in the mix.

Other spots in the field will be reserved for wild cards and the winners of the qualifying tournament, held July 27-28.

Competition gets under way in earnest July 29 and runs through Aug. 4.

The Citi Open, which is celebrating its 45th year, is one of 11 ATP World Tour 500-level events, a prestigious distinction reflecting the quality of an event’s field hand the size of its purse, and is regarded as a key tune-up for the season’s final Grand Slam event, the U.S. Open.