NEW YORK (AFP) - A sapling among the sequoias she may be but Melanie Oudin says it is not all about size. The 17-year-old American, at five foot six inches (1.69m) is small by modern day standards, especially compared to such towering figures as the Williams sisters or Russians Dinara Safina and Maria Sharapova. But that did not stop her from pulling off the biggest upset in the first four days of the US Open by defeating Russia's Elena Dementieva, five inches (17cm) taller than her, 5-7, 6-4, 6-3 to reach the third round. Oudin said former world number one Justine Henin was an inspiration to her as she worked her way through the junior ranks at a time when the Belgian regularly cut down players much bigger than herself. "The first thing is that she proved that you don't have to be six foot something to be No. 1 in the world," the former junior standout said. "But also, the way she plays, the way she moves, the way she uses all different shots and uses the entire court with her dropshot and her angles. "I mean, her one-handed backhand is so good. I don't have a one hander, but it's still OK. I just really like the way she plays. She figures out a way to take down these players that overpower her with her variety and her movement." Henin would have been proud of her devotee in the game against Dementieva, which lit up an Arthur Ashe Stadium court that was nearly empty when they started and nearly full 2 hours 45 minutes later when they finished. She soaked up the Russian's powerful baseline drives and then used her slice and drop shot to knock the bigger player out of her rhythm and comfort zone. Dementieva, a losing finalist here in 2004 and seen by many coming in to New York as the main threat to the Williams sisters, was fullsome in her praise of her conqueror. "I think she's very talented. She was playing very aggressively, really enjoying this atmosphere. "I think she moves really well. The footwork is really great. She was really fighting for every point, playing everything back. "She knows what is her strength. She's just waiting for the moment to attack the ball. "So even if she's not very tall, she's very athletic." The Dementieva win is the biggest to date of Oudin 's fledgling career but another big challenge could await in the fourth round should former US Open winner Maria Sharapova win her third round tie later in the day against another US teen Christina McHale.