"Do I look like Serena? Like, come on. Seriously?" Sloane Stephens understandably rankles at such a comparison with one of the world's greatest tennis players.

"You know, it's kind of crazy, but it's really not that bad. But when you hear it, it's like, 'Oh my god, did they just say that?' "

Only the laziest of observers could mistake the 19-year-old rising star for a Williams sister off the court. But on it, the similarities are striking.

Blessed with natural athleticism and steely determination allied to a powerful serve and forehand, Stephens shares many of the attributes that have helped Venus and Serena dominate the women's game over the past 15 years.

Posters of the sisters, who have won 21 grand slam singles titles between them, adorned Stephens' bedroom walls when she was growing up.

"I love them. Obviously they're like the coolest people. They are the greatest tennis players ever to me," she told CNN's Open Court.

Venus works really hard and is a great role model for girls, she says, while Serena has become a close friend.

"We talk about everything ... anything that comes to mind. We always have good conversations and we have a lot of things to talk about. So it works out."

2012 has been a breakthrough year in Stephens' fledgling career. She reached the second round of the Australian Open in January before making her Fed Cup debut for the U.S. alongside Serena against Ukraine in April.

Promising performances followed at both Wimbledon (reaching the third round) and at Roland Garros, where she achieved her best grand slam result to date, losing to U.S. Open champion Samantha Stosur in the last 16.

Results away from the grand slams have also been encouraging, with semifinal appearances at WTA events in Strasbourg in May and more recently in Washington D.C.

All of which has helped earn Stephens a top-50 ranking heading into the U.S. Open, where she meets Italy's Francesca Schiavone in the opening round on Tuesday.

The former French Open champion and two-time quarterfinalist at Flushing Meadows beat Stephens in Strasbourg and will provide a stern examination of the young American's evolving game.

"I'm working on so many different things. Coming to the net more, being more aggressive. I'm really working on my concentration. Staying focused. That's like a big one for me," she said.

Stephens has got a great attitude, says her coach David Nainkin, and doesn't fear the big stage.

"Sloane is a phenomenal athlete and probably has one of the best forehands in the world. She has so many options when she plays. So it's really about (improving) shot selection and channeling her power," Nainkin says.

"She's a great personality. She speaks very well ... she's fun to be around and she's great for tennis."

Stephens first picked up a racket when she was nine, catching the eye of coach and former men's pro, Francisco Gonzalez at the Sierra Sport & Racquet Club in Fresno, California.

On his advice, her mother Sybil Smith decided to relocate the family to Florida to further Stephens' ambitions, enlisting her at the Saviano High Performance Tennis Academy in Fort Lauderdale.

It was a smart move and provided the platform for a successful junior career which saw Stephens claim three consecutive junior grand slam doubles titles in 2010 at Roland Garros, Wimbledon and Flushing Meadows with Hungarian partner Timea Babos.

It was also proof of her exceptional sporting genes -- her mother was a champion swimmer at Boston University while her biological father, John Stephens, who tragically died in a car crash in 2009, was a former NFL running back.

Smith and Stephens divorced when Sloane was a child, and she saw little of her father while growing up. But his death, aged 43, was a painful blow and followed the loss of her stepfather to cancer two years earlier.

"When my dad died it was a really tough time, but my whole family has been super supportive. I've come out a better person and I've learned so much at a young age," Stephens said.

It was her stepfather who got Stephens hooked on tennis in the first place, Smith told CNN.

"He was very passionate about tennis. Sloane was always watching him at the club before we moved to Florida. The two of them really had a tennis bond," Smith said.