American teen Victoria Duval upsets former champ Samantha Stosur

Seventeen-year-old Victoria Duval dropped the first set to Australian Samantha Stosur, but the young American battled back to take the final two on Tuesday, pulling the biggest upset of the US Open so far.

Duval overcame 35 unforced errors for her first ever Grand Slam victory, 5-7, 6-4, 6-4.

The former US Open champion was on the ropes in the third set, with Duval serving for the match up 5-4. But Stosur fought off two match points before Duval's forehand winner buried the Aussie.

At times, Duval certainly showed her age and inexperience, but she was able to overcome both for easily the biggest win of her career. 

A partisan Flushing Meadows crowd rallied behind Duval, and the teen with a tiny voice thanked the patrons after the match -- only further endearing herself to them.

She also tried -- somewhat unsuccessfully -- to explain what was going through her head when she was serving for the match.

"I just tried to stay in the moment," Duval told ESPN after the match, before adding, "I don't know, I'm just really excited right now."