The plethora of tennis players on the ATP World Tour who have found themselves frustrated and despondent in the era of the Big Four should hang their heads no more.This week at the U.S. Open, Marin Cilic proved that anything is possible.The tall and lanky No. 14 seed steamrolled through his final three matches at this tournament without dropping a set. In the all-underdog final, he dismantled No. 10 Kei Nishikori, 6-3, 6-3, 6-3, in less than two hours to win his maiden major.Everything I was working for and dreaming came today, Cilic said, according to Christopher Clarey of The New York Times. And I feel for all those other players who are working hard, this is a big sign and big hope that if you are working hard things are going to pay off.For others wanting to follow in his footsteps, Cilic hascreated a guide to glory: Thoroughly prepare and believe that your best is good enough when the time comes. There was a time when the Big Four was so dominant that a blueprint like that wasn't enough, but that's not the case anymore.For Cilic, it was painstakingly simple in the end. An opportunity presented itself, and he seized the moment. Just like that, there's a new Grand Slam champion in men's tennis.To be fair, Stan Wawrinka showed the tennis world that the Big Four are human when he won the Australian Open this year, taking out Novak Djokovic, Tomas Berdych and an injured Rafael Nadal in the final. But while once could be a fluke, twice is a pattern.Cilic's win differs from Wawrinka's, though, because the Swiss star had a slow crescendo in the year prior to his Slam win and was ranked No. 8 when it began.The Croat was ranked No. 14 at the start of this U.S. Open, and though he had two titles this year, they were at much smaller tournaments and his overall results had been a bit erratic.Chris Chase of USA Today's For The Winsums up how unprecedented Cilic's run was:Since the dawn of the Open era in 1968, no player was a more unlikely U.S. Open champ than the 25-year-old Cilic. There have been lower-seeded players to win (Andre Agassi was unseeded in 1994, Pete Sampras was the 17th seed in 2002) but both were established stars whose rankings had slipped.Patrick Rafter, the No. 13 seed, was an unexpected winner in 1997, but that was a weak year of competition, with only one tennis greatPete Samprasin contention. Thats a far cry from winning a tournament that featured Roger Federer, Novak Djokovic and Andy Murray.Despite the come-from-nowhere vibe, Cilic is far from an unknown to tennis fans. He's been on the scene since he was a precocious teenager.With his flashy forehand, dictating backhand, nearly unbreakable serve and surprisingly deft movement despite his 6'6" frame, he convinced some fans and media members that he was the future of tennis.However, time and time again, Cilic was unable to establish himself as a real threat; he would mentally crumble at the biggest moments, particularly against the Big Four. He didn't have the self-confidence to push through.Then, a few things changed. First of all, last year he was suspended from the tour for four months for unintentionally taking a banned stimulant.(The ban was initially two years, but he appealed successfully). Instead of letting this down time ruin him, he used it to become stronger physically and mentally.Then, late in the year, he joined forces with fellow Croat and 2001 Wimbledon champion Goran Ivanisevic, who helped shore up his skill set and become passionate about the sport again. After his win in the semis, he ran through the improvements to his game, via Us Open.org.I feel in general I'm hitting the serve bigger, the shots are more compact, and I'm moving, I would say, very comfortably on the court. I'm able to run down some balls that I wasn't before. And even, you know, when I'm playing these long, long matches like the one with Simon, I'm able to recover quicker. So I feel that I'm -- I worked physically a lot. And also with Goran the intensity on the tennis court is pretty high. So I feel, you know, everything with that adds up to, you know, being better in all aspects.But what seems to have pushed Cilic's development over the edge was beliefa belief that started after seeing Wawrinka win the Australian Open, and carried Cilic throughout an up-and-down season."When I'm playing now these bigger matches I feel like if I'm going to play well I have a good chance," he told the New York press. "Wawrinka opened the doors for us from the 'second' line, and I think most of the guys have now bigger belief that they can do it on the Grand Slams."Cilic's physical enhancements pulled him through the first few rounds of this tournament, particularly his grueling and drawn-out matches in the third round against Kevin Anderson and the fourth round against Gilles Simon. After that, his talent and belief took over.Playing what he told Mary Joe Fernandez on CBS was the best tennis of his life, he took out No. 6 Tomas Berdych, No. 2 Roger Federer and then Nishikori in straight sets. In the final, he served 17 aces and hit 38 winners to only 27 unforced errors. He was a machine.Those who have watched Cilic over the years have seen him play out-of-his mind tennis for portions of matches against the top players, but he would always fade.For at least this fortnight, that was anything but the case.For others who are looking to hoist a major trophy, that's the keyput in the hard work physically and technically, and then, when your opportunity comes, don't overthink it. Believe that your best tennis is enough. Let go of the doubts and just play.The members of the Big Four aren't going away. They'll win more Slams and provide many more days of frustration for the dreamers of the ATP Tour. But there are more cracks in their facade than ever before.There are going to be more opportunities. There's going to be glory left on the table for the taking. It's up to the rest of the ATP to step up and take itafter Cilic's run, they've certainly been shown the way. Click here to read full news..