By Martyn Herman
LONDON (Reuters) - The problem with allowing a bunch of rowdy gate crashers into the party is they will repay you by re-arranging your furniture.
It must feel a little bit like that for the established names at this year's Wimbledon.
After loitering on the edge of the action for a few years, the likes of Bulgarian Grigor Dimitrov and Canada's Milos Raonic are clearly fed up waiting for the older guys to go home.
And as for Australian wild thing Nick Kyrgios, he just booted down the door and strutted his stuff on the dancefloor.
Tennis, it seems, is in the throws of a revolution.
Not just in the men's game either.
Canadian Eugenie Bouchard, 20, and Romanian Simona Halep, just a couple of years her senior, will meet in the Wimbledon semi-final on Thursday with both tipped to start collecting grand slam silverware before too long.
America 19-year-old Madison Keys is another fast-riser.
It would be foolhardy to discount the likes of 17-times grand slam champion Serena Williams, Maria Sharapova, Li Na and Victoria Azarenka, who have shared out the major silverware in recent years, but a change is in the air.
Most intriguing though is the attack on the established inner circle in the men's game where the "big-four" of Rafael Nadal, Novak Djokovic, Andy Murray and Roger Federer have, at times, appeared to be playing a different sport entirely.
Between them they have won 35 of the last 37 grand slams of offer, with the bulk going to Federer and Nadal.
Only the injured Juan Martin del Potro and Swiss Stanislas Wawrinka have disturbed the status quo in that time but cracks are appearing and what is more, the top guns know it.
The 23-year-old world No.13 Dimitrov, a player with gifts similar to 17-times grand slam champion Federer has long been talked about as the "real deal" without backing up.
Until last October the man they used to call "Baby Fed" had not won a title. Now, with coach Roger Rasheed putting the pieces of the jigsaw together, he has four and on Wednesday he spread his wings on Wimbledon's Center Court to annihilate reigning champion Andy Murray.
His 6-1 7-6(4) 6-2 victory came less than 24 hours after world number one Nadal was played off court by 19-year-old wildcard Kyrgios - a stunning result that made front page news across the world and had the likes of John McEnroe calling him the new Boris Becker.
Federer, whose enduring quality has taken him in sight of a record eighth Wimbledon title, likes what he sees.
"I mean, it's exciting for the game to see new faces like Kyrgios, now Raonic or (Kei) Nishikori," he told reporters when asked for his views on the rise of the young guns.
"There's been a few guys knocking on the door now. I think it's good times in tennis. There's a lot of excitement."
The 27-year-old Djokovic, who battled past Marin Cilic to set up a Wimbledon semi-final against Dimitrov, said it was about time a new generation began to exert some real pressure.
"We have Kyrgios, Raonic. Kyrgios just got into the mix in this tournament. He's a 19 year old, which is amazing. It's good for tennis to see that, because we lacked a little bit of successful teenagers in the last 10 years or so.
"We have these youngsters coming up, fearless on the court, hitting the ball, not caring who is across the net.
"It's good. It gets more attention to new faces and to new wave of generation that is able to challenge the best and be contending for grand slam titles."
Murray became Dimitrov's first top-10 victim in a grand slam on Wednesday and the nature of his beating prompted him to suggest he needed to go away and improve if he is to keep pace with the fearless ball strikers now on the march.
"If you play against a player like a Kyrgios or Dimitrov or Raonic and you don't play very well, it's tough to win," he said.
"Whereas before maybe when they're younger and a bit inexperienced you can still find ways to come through.
"But now that they're getting more experience and improving, it's tough to do that."
Raonic, a 23-year-old with a choir boy face who smacks down serves at 135mph, ended Kyrgios's Wimbledon adventure to reach his first grand slam semi-final on Wednesday.
Afterwards he said the clock was ticking for the big four.
"It's a thing I guess that you can't really out-run time," Raonic, who will set his sights on 32-year-old Federer on Friday, told reporters.
"New guys got to come up and they've got to step up. We've been doing better and better, especially this year.
"It's good to be a part of it. It's good to see the human side to those four guys when you have to step up to face them.
"Have a belief more than ever that it's yours for the taking if you play well."
(Editing by Greg Stutchbury)