NEW YORK – While 15-year-old American CiCi Bellis was in the process of stunning a Grand Slam-tournament finalist to become the youngest player to win a U.S. Open match since 1996, her father tried to conceal his emotions courtside.

Like many a teen, CiCi has strict rules for Dad in public — even if his 1,208th-ranked daughter is pulling out a back-and-forth 6-1, 4-6, 6-4 victory Tuesday over 12th-seeded Dominika Cibulkova of Slovakia in the first round at Flushing Meadows.

“I’m told I cannot sigh and I cannot move or say anything (because) that distracts her, so I just have to sit there like a Sphinx and just smile and pray,” the elder Bellis, Gordon, explained with a deadpan delivery. “She hears me when I sigh. So I can’t sigh.”

Ah, yes, the joys of raising kids. And make no mistake, Bellis is a kid. She is home-schooled and about to start 10th grade. Her first memory of the U.S. Open is watching on television while Maria Sharapova played. She likes to hang out at the mall with friends back home in California.

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Asked whether she is a fan of pop star Justin Bieber, Bellis answered, “I used to like him when I was younger, a couple years ago.”

Her victory over this year’s Australian Open runner-up was the most surprising of the afternoon session on the second day of the year’s last Grand Slam tournament.

In the night session, two-time defending champion Serena Williams beat Taylor Townsend 6-3, 6-1 in a matchup of Americans after Roger Federer of Switzerland beat Marinko Matosevic of Australia 6-3, 6-4, 7-6 (7-4). Basketball legend Michael Jordan sat in Federer’s guest box at Arthur Ashe Stadium.

“Growing up, he was my big sporting idol,” Federer said. “Having him here is unbelievably special.”

Aside from the Williams sisters, Serena and Venus, U.S. tennis fans have not had much reason to cheer for their own in the latter stages of major tournaments lately. That’s why the occasional run by a young U.S. player — think Melanie Oudin, wearing “Believe” on her shoes in 2009 — stirs interest at Flushing Meadows.

“Believing was the number-one thing that I had to do today,” Bellis said. “That’s what my coach told me before the match also: Just go out there and believe that you can win.”

Bellis is young enough that she plans on playing in the junior tournament here. She lost in the third round of that event a year ago; she lost in the first round of the Wimbledon girls’ tournament this summer.

Not since Russian Anna Kournikova was 15 in 1996 had someone so young won a match at the U.S. Open. And not since Mary Joe Fernandez was that age in 1986 had an American done it.

Bellis next plays 48th-ranked Zarina Diyas of Kazakhstan.

“Now it’s time for her to refocus, not get too excited about this first round. Just get back to business,” Fernandez, an ESPN analyst these days, said of Bellis.