By Julian Linden
BRISBANE (Reuters) - Roger Federer knows the next generation of tennis players are closing in fast on the Big Four, the so-called elite quartet who have dominated the last decade of men's tennis.
Federer himself has not won a grand slam title since 2012 and the other members of the troupe, Rafa Nadal, Novak Djokovic and Andy Murray, have all been battling injuries and illness.
Their drop in form and ailments have coincided with the rise of a new crop of players challenging in the majors, a sign that perhaps their era is coming to an end.
Stan Wawrinka won last year's Australian Open and Marin Cilic won the U.S. Open -- marking the first time since 2003 that two players outside the Big Four won grand slam titles in the same season.
But Federer is not convinced that the changing of the guard is imminent. On the contrary, the 33-year-old Swiss believes last year's results were an anomaly and normal service will resume in 2015.
"We have had some injuries, it's not because we didn't play well or that we maybe dropped a bit," he told reporters at the Brisbane International on Friday.
"Rafa had his issues, Murray had surgery on his back, I've had a tough year in '13. The only guy who was really consistent was Novak ... and he took care of it and took advantage of it to some extent. He was still there when it mattered the most."
Djokovic finished 2014 ranked number one in the world. His season featured a second title at Wimbledon, where he beat Federer in an epic final.
Nadal won the French Open for a record ninth time before injuries stalled his season. Federer won five ATP tournaments, including the Cincinnati and Shanghai Masters events and finished year ranked second.
"Rafa was still there again on clay. I was consistent last year. I think Murray is on his way back. He still made the Masters, even though he didn't play so well for sometime," Federer said.
A new wave of players also emerged last year. Kei Nishikori made the U.S. Open final while Milos Raonic and Grigor Dimitrov reached the semi-finals at Wimbledon.
The young trio have all made a strong start to 2015, joining Federer in the semi-finals at Brisbane while Djokovic and Nadal suffered early defeats at the Qatar Open.
Federer is impressed by his young rivals but not ready to anoint them just yet, saying they may have to wait a little longer than most people think.
"It's still a bit early to say. We'll see again what's going to happen this year," he said.
"I do believe there is a group of guys right there that can make a break again and can do special things. I just think it's too early to say in the season just because Novak and Rafa lost in Doha that there is something on the horizon.
"I don't read into any of those results. I think they are going to be tough to beat, and favourites for the Australian Open, to be honest."