Sandra Harwitt Special to USA TODAY Sports Published 7:31 AM EST Jan 24, 2019 MELBOURNE — Twenty-year-old Stefanos Tsitsipas, the newest sensation in men’s tennis, discovered in the Australian Open semifinals that youth can only take you so far. Any notion that Tsitsipas had that he might become the third player in history to defeat Roger Federer and Rafael Nadal at the same Grand Slam ended on a hot Thursday night where the temperature was still 96 degrees Fahrenheit. The 32-year-old Nadal showed the Greek why he’s a 17-time Grand Slam champion, schooling him 6-2, 6-4, 6-0 in a near-flawless performance where he mixed up play to keep Tsitsipas off balance. “Honestly, I have no idea what I can take from that match,” said Tsitsipas. “It’s not that I was even close to get to something. I only got six games from that match. “He has this, I don’t know, talent, that no other player has. I’ve never seen a player have this. He makes you play bad. I don’t know. I would call that a talent.” This is the 10th time in Nadal’s career he has reached a Grand Slam semifinal without losing a set. He’s now reached the Australian Open final on five…