Two of the Big Four have lots to prove when the U.S. Open begins today at Flushing Meadows in New York. Defending champion and No. 2-ranked Novak Djokovic would certainly like to win his second major of the year to affirm that the success he had in 2011 — three Grand Slam titles — wasn’t a fluke. And for Andy Murray, still without a major, it’s time to back up his Gold Medal at the London Olympics and win his first Slam. Roger Federer really has nothing to prove at the last major of the year. The 31-year-old Swiss won his first Slam in two and a half years at Wimbledon, regained the No. 1 ranking after the fortnight at SW19, and has won an ATP Tour high six tournaments in 2012. Rafael Nadal is on the shelf recovering from a knee injury. For the No.4-ranked Murray, the stakes at New York are perhaps the highest. The 25-year-old Scot has lost four times in Grand Slam finals. But after thumping Federer in the Olympics final earlier this month, Murray should be brimming with confidence. “Obviously winning the Olympics was the biggest win of my career, that’s for sure,” said Murray in New York on Saturday. “It meant a lot to me. I feel confident in myself just now. That’s what’s important. But I needed to make sure that afterwards, I worked hard. That’s the most important thing.” Based on the year he’s had, and current form, Federer should be a slight favorite in New York. The Swiss Maestro defeated Djokovic handily in the final of the Cincinnati Masters a week ago, regaining his mojo following the Olympics. Federer, at the top in the First Quarter of the draw, could see his first challenge from either No. 16 seed Gilles Simon or No. 23 Mardy Fish in the fourth round. No. 6 seed Tomas Berdych looms as his opponent in the quarterfinals. Murray, the No. 3 seed, heads the Second Quarter and is slated to meet No. 15 seed Milos Raonic in the fourth round and Jo-Wilfried Tsonga, seeded No. 5, in the quarterfinals. With Nadal out, No. 4 seed David Ferrer tops the Third Quarter, in the most wide-open section of the draw. Ferrer is seeded to meet No.13 seed Richard Gasquet or No. 21 Tommy Haas in a fourth-round matchup, and Janko Tipsarevic, the No. 8 seed, in the quarterfinals. My hunch, though, is that No. 9 seed John Isner will take out Tipsarevic in the fourth round. Djokovic, the No. 2 seed, is top dog in the Fourth Quarter. Nole should meet No. 14 Alexandr Dolgopolov in the fourth round and No. 7 Juan Martin del Potro, if his wrist holds up, in the quarterfinals. It’s pretty hard to go against any of the top three seeds. I see the semifinals as Federer versus Murray and Djokovic against Isner. No predictions beyond that, yet.