Seven-time Grand Slam winner Novak Djokovic remains a favorite at the upcoming U.S. Open, but a new generation of potential tennis stars is aiming to break through. (Andy Lyons/Getty Images)

There seemed to be optimism for many men’s tennis players after the first Grand Slam of the year, a hope the same trio wouldn’t keep winning everything. The gap between Rafael Nadal, Novak Djokovic and Roger Federer and everyone else appeared narrower after Swiss Stanislas Wawrinka won the Australian Open.

But that was dashed when the usual suspects claimed the next two Grand Slams, Nadal taking the French Open and Djokovic winning Wimbledon.

Players are divided on whether there’s an opening for new faces to break up “The Big Three.” With Nadal out for the U.S. Open, the final Grand Slam of the year that begins Monday, there’s hope again.

“There’s too many players hungry and sort of licking their chops and trying to create those opportunities,” sixth-ranked Milos Raonic said earlier this month. “People are sad he’s not there, but there’s nobody losing sleep over it because people want those opportunities.”

The Canadian has had a strong summer hard-court season, winning the Citi Open in Washington and advancing to the quarterfinals in Toronto and the semifinals in Cincinnati. Raonic and fellow 23-year-old Grigor Dimitrov (No. 8) were Wimbledon semifinalists and are the young stars that most expect to be the next generation of Grand Slam-winning regulars.

With his favorite surface being hard court, Raonic said he expected to play better at the U.S. Open than he did at Wimbledon, where he fell to Federer in the semifinal. Raonic took a not-so-subtle shot at Federer, a decade his senior, when he said that outside of the top two spots occupied by Nadal and Djokovic, the rest, “this year specifically, are up for grabs.”

While No. 14 Richard Gasquet thinks the young players such as Raonic and Dimitrov are playing well, he says it’s not their time yet.

“I think the top four are still better,” Gasquet said. “In the future, next year or two years, I think it can change. But for [now], I’d say it’s a little bit early.”

There’s debate on whether a top four still exists. Though Wawrinka has stayed in the top four since winning the Australian Open in January, his results have been inconsistent. After winning Wimbledon in 2013, Andy Murray has gone from being ranked second last summer to ninth. Murray could face Djokovic in the U.S. Open quarterfinals.

If momentum decides the U.S. Open winner, then Federer would have it secured. The Swiss reached the final at the Rogers Cup in Toronto and won an unprecedented sixth Western & Southern Open title in Cincinnati. Jo-Wilfried Tsonga beat an impressive field to win the Rogers Cup: Djokovic, Murray, Dimitrov and Federer, consecutively.

No. 7 Tomas Berdych has been ranked in the top 10 for most of the last four years, and he disagrees that there’s an opening at the top of men’s tennis. Sure, Wawrinka had a great run at the Australian Open, but since then, Berdych said “it’s back in the old lines, how it was before.”

Whether or not things have actually changed, the perception that change is coming could be enough for someone new to win the last Grand Slam of the year.

“The top three are still the top three in the world,” top American John Isner said. “They’re not going to go away, but I think maybe the gap has closed a little bit. I think that’s in large part due to other players believing. That’s the most important thing when you go up against a guy like Rafa, Roger or Novak. You just have to believe that you can beat those guys, and I think players are more and more showing that belief.”