US Open champ Sloane Stephens 'shocked' about her remarkable win

— -- U.S. Open champion Sloane Stephens, who just last month was ranked 957th in the world, spoke out about her remarkable win this weekend, saying she felt "shocked," and crediting her mother's support as a major factor in her success.

"I always wanted to win a slam," Stephens said in an interview with ABC News' Robin Roberts. "I always thought about it, but I never like ... pictured myself in that situation. Winning the last point ... when it happened I was like, 'Wait, what do I do now? Do I cry? Do I roll on the ground?' I was just so shocked."

Stephens said her victory has not fully sunk in yet.

"I'm still like, 'Oh, this is so fun,' and my Mom's like, 'you know you won the U.S. Open,'" Stephens said.

"Parents don't get enough credit," Stephens added. "Even if your kid is the worst athlete in the world, they're like, 'You're great.'"

She said that she credits her mother for contributing to her success, saying, "I just wanted people to know your kid could be me if you just have an awesome parent."

Stephens' mother, Sybil Smith, told ABC News that as a parent, "That's what we do."

"We support, we love unconditionally," Smith said. Smith said that she felt so proud of her underdog daughter "from the very beginning."

"I watched every point and it was just exciting, but I was so proud from the first point, that she got out and fought. ... That made me feel good," she said. "She was on her way to her goal. ... No matter what happens she was there, she made it. I was on pins and needles the whole way but I was just proud from the very beginning."

Stephens also opened up about taking time away from tennis while she was injured, saying she used that time to live life to the fullest outside of her tennis career.

"I always feared that I was missing out ... weddings and baby showers, and I think in the 11 months that I was out, I did everything humanly possible," Stephens said of her time off. "I went everywhere, I saw all of my friends, I did everything. And I think I lived enough that 11 months to last me five years."

Stephens, who missed last year's U.S. Open due to a foot injury, says that she did not perform as well as she had hoped during her run at Wimbledon.

"I was like, 'Eventually I'm going to beat somebody, so it's just a matter of time,'" Stephens said. "Then coming into the U.S. Open I was like, 'Wow, I'm playing really good.' This is shocking because this was my fifth tournament back."

"I did an interview with someone four days before the final, and they were like, 'You know in four days you could win the U.S. Open,' and I was like, 'Really? Me? Wow.'"

Stephens added that in addition to winning the U.S. Open, another highlight from this weekend was having her tweet go viral.

"Did you see how many retweets that got?" Stephens said. "Like, 'Mom, I've made it! Seriously!'"

"This is insane," she added of her tweet. "So many people ... they know I exist?"

The tennis star added that since her win she met fashion designer Vera Wang, "and it was the greatest thing ever."

"I asked her to design my wedding dress and she was like, 'Of course,'" Stephens said, but emphasized that despite asking Wang, she is not yet engaged.

Stephens is reportedly dating American soccer star Jozy Altidore.