London: Roger Federer said the domination of tennis's Big Four made it incredibly tough for up-and-coming players to get anywhere near them.
Novak Djokovic, Rafael Nadal, Federer and Andy Murray have dominated the big events in recent years and the Swiss great said it was all down to hard work and talent.
While Murray has yet to win a Grand Slam title, world number three Federer said he was right up there in the sport's elite class.
Asked what the biggest factors were in their domination, six-time Wimbledon champion Federer said: "Mental, physical, and talent, putting those three things together.
"It is incredible to what degree we have been able to not only win the slams, but also in the Masters 1000s.
"You can include Andy Murray to those as well because he's won a ton of those. It seems like it's really hard for other players to break through really on a slam level or a Masters 1000 level.
"It's interesting. It shows how solid we've been over the last years, how hard it is to break through, but how hard it is to stay at the top.
"I put it down to hard work, talent, and again the mental and physical abilities to also win on poorer days."
Third seed Federer beat Spain's Albert Ramos 6-1, 6-1, 6-1 on Monday to reach the Wimbledon second round, taking just 79 minutes to kick off his bid for a record-equalling seventh title.
The record 16-time Grand Slam title winner will face colourful Italian Fabio Fognini for a place in the last 32.
The world number 68 beat France's Michael Llodra for a place in the second round.
Federer used to hit with Fognini when the Italian was a junior and the Swiss was about to top the world rankings.
"I do remember the time we did practice together because I very often do practice with juniors coming through the rankings who are there in the second week," the 30-year-old said.
"So on the days off I practice with a lot of juniors, and then also maybe warming up for bigger matches. They're around, they're excited, and so it's a win-win situation for all of us.
"I do remember him back then. When they make it on tour, I'm very happy for them. Not that I had anything to do with them, just that it's nice to see them again. We had one match in Montreal. He didn't have a very good match. I beat him very comfortably.
"I see he's very talented, a great shot maker. That's why I was not very surprised he was able to beat (Michael) Llodra today, who you would probably favour on a grass court. He does have a lot of talent.
"He's definitely got the talent to be a very tough opponent. Better be ready for some good shots coming my way."
Federer said he appreciated being back at Wimbledon, which has resisted the drive for thumping music, loud announcers or other substitutes for genuine courtside atmosphere.
"It's absolutely special, because you do realise the moment you walk onto the court that it is a different place here than any other," he said.
"Just the respectful clap, no music. The whole thing is very much focused on the players and on the sport, which is beautiful."