Latvia's Anastasija Sevastova ousts No. 3 Garbine Muguruza

Sevastova emotional after huge win (1:47)

Anastasija Sevastova is emotional and thrilled to have won a night match in Arthur Ashe Stadium. Sevastova advances to the third round at the US Open for the first time with an upset win over Garbine Muguruza. (1:47)

NEW YORK -- French Open champion and No. 3 seed Garbine Muguruza was stunned Wednesday night by a player who was recently out of tennis for 18 months.

Anastasija Sevastova, a 26-year-old from Latvia, recorded the US Open's biggest upset so far, defeating Muguruza 7-5, 6-4 at Arthur Ashe Stadium. It was the first time Sevastova has ever beaten a played ranked among the top five.

Muguruza saved three match points before Sevastova broke her after failing to serve out the match twice. That brought Sevastova to tears.

When told on court she had scored the biggest victory of her career, based on rankings, on the world's biggest court, Sevastova looked amazed.

"Really?" she said.

And then most of an expletive slipped from her mouth.

"I was shaking a little bit," Sevastova continued. "It's amazing. In Ashe, in night match? What's going to be bigger?

"I have to solve my head, myself, all the thoughts -- what could be? What could not? I am so happy."

Sevastova was ranked as high as No. 36 among WTA players in 2011, but a series of back injuries led to a period of depression that saw her leave the game in 2013-14.

How big was this upset? Playing mostly ITF events and trying to qualify into WTA main draws, Sevastova has won only $275,000 in prize money this year.

Muguruza, meanwhile, has collected more than $2.8 million.

"I don't think about the French Open any second. It's past," she said. "Everybody's looking forward to the next one, the next tournament."

Since winning her first major title in Paris at the age of 22, Muguruza has struggled with her sudden success, similar to some of her other peers, such as Simona Halep, Sloane Stephens and Eugenie Bouchard. Muguruza has a post-Roland Garros record of 6-6. She needed three sets to beat qualifier Elise Mertens in the third round.

Ironically, Sevastova studied leisure management in Austria while on sabbatical. She'll have little free time the rest of this week. She faces Kateryna Bondarenko, a three-set winner over Saisai Zheng, in a third-round match Friday.

Her mother, an English teacher back in Latvia, is with her in New York, the first time she has ever traveled to a Grand Slam. She's supposed to go home Thursday, though now Mom wants to stay.

Sevastova's best friend is in town, too.

"We'll maybe go somewhere," Sevastova said of what celebration might be in the works. "They will drink -- I will watch."

Information from The Associated Press was used in this report.