The Swiss master will drop out of the top four for the first time in a decade, but new pretenders are a little thin on the groundLONDON - It is fitting that tennis should be hurled into minor turmoil at its oldest and grandest tournament because, paradoxically, it is at Wimbledon where change has often been embraced most eagerly.The 127th edition of the event will be remembered for many things, not least the early departure of its seven-times champion Roger Federer, a cataclysm that invited speculation about his future and who might covet his parking space at the All England Club, his second home.Federer will drop to No5 in the world rankings a week on Monday, the first time he has dipped out of the top four in 10 years. He is nearly 32 and, although in the moments after losing to Sergiy Stakhovsky on Wednesday night he committed himself to playing on "for many years”, the fear is that this is bravado built on hope and maybe a little trepidation. Tennis has been his life. He is not ready to let go just yet.Rafael Nadal, who left Wimbledon bruised on Monday, edges up to No4, behind David Ferrer (who, perversely, has lost to Federer 14 times in a row, and 20 times in 24 to Nadal) and the two players of the creaking Big Four who have yet to crack, Andy Murray and Novak Djokovic.What was likely only a few weeks ago is now less so. Will Federer add to his 17 grand slams? Will Nadal’s left knee collapse again, as it did against Steve Darcis? Will they even still be with us next June? They say they will and everyone hopes they are right, because they have provided engrossing rivalry for a decade, with Murray and Djokovic latterly the most brilliant of understudies.Yet there is an undeniable mood of uncertainty in the air.Murray said after watching the last moment’s of Federer’s match he had not experienced a week like this. "These sorts of upsets happened a lot more 10 or 15 years ago,” he said, "but, since I came on the Tour, Rafa and Roger have always been in the latter stages of the slams. Obviously Novak the last few years and I have played consistently well in the slams too the last few years but it will be the first time in a long time that Rafa and Roger haven’t been in the third round of a slam.”The former player and broadcaster John Barrett, who played here for 18 years, has seen more tennis in these grounds than anyone since 1946 and his revised third edition of "Wimbledon, The Official History” records all of it and more."Yes, I think there is a changing of the guard,” he says. "It is 10 years since Roger first amazed us with his artistry. But nothing goes on forever. The surprise is that it has lasted as long as it has, at such a high level. His consistency has been quite staggering and there has been nothing even approaching it and I don’t think there ever will be. In 19 consecutive grand slams he reached the final 18 times. That is absolutely phenomenal. And Nadal lifted him. Tennis always needs great rivalries.”Barrett thinks Murray and Djokovic are "the natural inheritors” but there is an obvious chasm to fill below them. The contenders are not quite ready, he agrees, and the incumbents refused to go quietly. On day four the young Canadian Milos Raonic went out in three sets and the former US Open champion Juan Martín del Potro got through to the third round, but made heavier work of it than he might have done against the Canadian Jesse Levine, ranked 112 in the world and who has lost four of 14 matches this year. Elsewhere there was rain, slippery grass and doubty work of it.Romantics, meanwhile, who thrilled to the spectacular exploits of the exquisite serve-and-volleyer Sergiy Stakhovsky against Federer on Centre Court on Wednesday night were briefly encouraged to wonder if this fading art was about to be revived.John McEnroe, a kindred spirit, hopes so, but with no conviction. Watching Stakhovsky hustle Federer out of the tournament behind a big serve and 61 points secured in 96 visits to the net gave him "goosebumps”, he said. But McEnroe’s belief that Raonic might one day leave the baseline and start to look like Pete Sampras is a little way from fruition, as was witnessed on Thursday.Raonic leaves here chastened. There are still a few pretenders in the hunt. It will be a fascinating second week.