Updated

No. 3 seed Sloane Stephens and James Blake survived three-set fights in their opening matches at the Citi Open on Monday. Fellow Americans Melanie Oudin and Brian Baker weren't so fortunate.

Stephens defeated Sesil Karatantcheva 6-3, 2-6, 6-1, while Blake rallied from a set down for only his second tour win of the year, advancing to the second round with a 4-6, 6-2, 6-2 triumph over No. 5 seed Pablo Andujar.

Up an early break in both the first and third sets, Oudin fell 6-4, 6-7 (2), 7-6 (5) to Aravane Rezai. Baker, who made a surprising run to the round of 16 at Wimbledon in June, couldn't capitalize on a good start in losing 4-6, 6-3, 6-4 to Florent Serra.

No. 2 Chanelle Scheepers and fifth-seeded Barbora Zahlavova Strycova also lost first-round matches at the Citi Open, a staple on the ATP schedule that is combining with the WTA Tour for the first time.

Stephens lost the final three games of the second set, including two on her own serve, but opened the third by breaking Karatantcheva twice for a 3-0 lead. The 19-year-old American tacked on two more breaks to advance.

"It was just a matter of a couple of loose points and some weird calls and things that happened," Stephens said of the rough middle set. "I was just a little more consistent in the end and I think that's what carried me through."

Stephens reached the fourth round at the French Open and the third at Wimbledon this year. The Floridian narrowly missed a berth on the U.S. Olympic team, and since Wimbledon has made first-round exits in her last two tournaments. There was no denying that avoiding an unwanted hat trick crossed her mind.

"You just can't ever lose three in a row, that's all," Stephens said. "That's not even an option."

The 32-year-old Blake's 2012 campaign had been a losing one entering Washington, site of his first title 10 years ago. Coming off knee surgery in November, he lost eight of his nine matches this year.

"I think I was a little falsely optimistic earlier in the year," Blake said. "I really thought I was able to get out there and compete. I don't have the ability to compete with these guys unless I'm 100 percent. . My legs feel great now."

That showed starting in the second set as Blake used his return of serve and eight aces to carry the day.

"Second set, right from the start I started feeling good, got a rhythm and never let go of that," Blake said. "I felt like I was in the games. I was sort of dictating most of the time and that's the way I want to play."

Mardy Fish, the top-seeded man, is scheduled to play his opening match on Tuesday. Fish, the No. 13 ranked player, skipped the Olympics after missing several weeks on tour earlier this year following a procedure to correct a heart problem.

Russian Anastasia Pavlyuchenkova is the top seed in the women's draw.

Scheepers, ranked No. 42 in the world, fell 6-2, 6-1 to Magdalena Rybarikova. Zahlavova Strycova was beaten by Edina Gallovits-Hall, 7-5, 4-6, 6-3.

No. 7 seed Coco Vandeweghe beat Olga Govortsova 6-4, 6-1 and No. 8 seed Olga Govortsova topped Karolina Pliskova 6-2, 6-2 to advance to the second round.

Playing his first full season on tour season since 2005 after missing time with an assortment of injuries and surgeries, the 27-year-old Baker started the year ranked No. 456. His success at Wimbledon combined with solid performances on clay courts helped propel the former juniors star into the top 100 this month. Since then, he has had three straight opening-round losses, all on hard courts.

"Fitness wise I was fine today. It was not an issue," said Baker, who already has earned a place in the upcoming U.S. Open. "I definitely took some time off after Wimbledon, had some aches and pains. It hasn't been the physical aspect of it. It's just been maybe more the mental aspect, coming back from such a high."

Baker broke Serra's serve twice in the opening set to take a commanding 5-2 lead, but lost his own serve at 3-4 in the second en route to losing that set. In the third, Serra needed just five points on Baker's serve for a 1-0 lead, broke again to make it 4-1 and won as Baker's final backhand sailed wide.

"All summer I played pretty clean matches and was still able to be aggressive when I should have," Baker said. "Today was definitely not my day."