Sloane Stephens leads a cast of rising ...

Sloane Stephens returns a shot to Angelique Kerber, of Germany, during their match at the BNP Paribas Open tennis tournament, Friday, March 9, 2012, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

New expectations mean new challenges for new tennis stars.

Sloane Stephens found out at Indian Wells in February, the No. 16-ranked player in the world having to explain herself after a loss to Poland’s Urszula Radwanska.

For Stephens, 20, it was her first match on American soil since she stunned top-ranked Serena Williams in the Australian Open quarterfinals.

“Just struggling,” Stephens said after her early exit from the California tournament.

She pointed out that an early round night match was different for someone familiar with playing in the morning on “Court Timbuktu back there.”

“It’s definitely tough,” Stephens said of the upset. “But I guess that’s just what happens when you’re slightly good.”

Adversity in rarefied rankings air is fair trade-off for young U.S. players and their American fans waiting patiently for the post-Williams wave of top talent.

Stephens is leading an American charge that also includes Family Circle Cup participants Vavara Lepchenko, Christina McHale, Jamie Hampton, Madison Keys and Melanie Oudin.

Lepchenko is 26, the others are 23 or younger.

“I’m really happy that the American ladies are stepping up and doing pretty good,” Serena Williams, 32, said at the Australian Open.

Stephens grew up in South Florida with a poster of Serena in her room, and an exceptional athletic edge. Her mother Sybil was a standout swimmer at Boston University. Her father John Stephens was an NFL running back for the Patriots, Chiefs and Packers from 1988-1993. She learned tennis from her stepfather, Sheldon Smith.

Pain has also been part of the growing process for Stephens. Her stepfather died in 2007 after a two-year fight with cancer. Her father died in an auto accident in 2009.

But the 5-7, 135-pound Stephens has grown into a poised woman with a well-rounded game suited for any surface. She was showing potential at the 2011 Family Circle Cup — known for attracting rising stars from all nations — when she lost to Shuai Peng in the Round of 64.

“It’s been fun, but all I wanted to do is play tennis,” she said at Indian Wells, when asked about the notoriety that followed her Australian Open performance. “I don’t care about all this other stuff. I just want to be on the court, have fun, enjoy myself, play like how I played in Australia. And just do what I was doing before all this happened.”

Melbourne certainly was magical. Though Serena Williams was nagged by back problems at the Australian Open, the favorite took the first set. It was by far the biggest win for Stephens, still looking for her first WTA singles title.

“I think I was convinced that I was able to do it when I lost serve in the first game in the second set and I went down 2-0,” Stephens said. “And I was like, ‘Hmm … this is not the way you want it to happen.’ But you just fight and just get every ball back, run every ball down, and just get a lot of balls in play, From then on I got aggressive, started coming to the net more, and just got a lot more comfortable.”

Stephens and the other young Americans have spent the last few formative years playing against each other and as teammates.

Stephens, McHale, Lepchenko, Oudin and Hampton have played on various U.S. Fed Cup teams since 2011.McHale and Lepchenko joined the Williams sisters on the 2012 U.S. Olympic team in London.

Two of the players were born abroad, Lepchenko in Uzbekistan and Hampton on a U.S. Army base in Germany. Lepchenko has lived in the U.S. since 2001 and became a citizen in 2007.

McHale has something of a reverse international twist. She was born in New Jersey, but as a 3-year-old moved to Hong Kong with her family when her father had a job transfer. McHale began playing tennis at a Hong Kong condo complex and moved back to the U.S. at 9.

Lepchenko vaulted from 110 in the WTA rankings after 2011 to 21 last year. Hampton, No. 64, jumped from 171 in the 2011 rankings to 77 in 2012. Oudin had great runs at the Family Circle Cup in 2010, reaching the quarterfinals (lost to Vera Zvonareva) and in 2009, reaching the Round of 16 (lost to Marion Bartoli).