The greatest double act in sport's history

When the Williams sisters make their bow at Wimbledon this week we will be watching the greatest-ever story in tennis. And quite possibly, if Venus and Serena remain at numbers one and two and win more titles, it will become the greatest saga ever, in any sport.

There is simply nothing to compare with a yarn which has everything. Their father, Richard, who had never played the game, never even seen the game apart from watching it on television, says to his wife: "We are going to have two more kids and they are going to be world champions." The girls lived in East Los Angeles, where they practised with street gangs surrounding them, and one of the gangs literally protecting them.

Then Richard said they would become world numbers one and two. And they have done just that. If it were not for the fact that they are black, this story would have been three times bigger than it already is. Just imagine how many more magazine covers they would have been on. Imagine the commercial prospects, it would have been on the level of David and Victoria Beckham.

I am biased, perhaps, because tennis is my game, but tell me another story like it, whatever the sport. Venus and Serena could be the top two for the next five years, or they could decide to do something else. Their father is definitely a wacky guy but the kids seem to have turned out pretty normal – they are well educated and they carry themselves pretty well.

After the French Open, where the sisters swept the board with Serena beating Venus in the final, the Wimbledon women's event shapes up as a three-horse race. Jennifer Capriati, winner of three Grand Slams in the last year and a half, cannot be discounted but she will have to beat both sisters to lift the title. If they stay at number one and two any challenger is going to have to do that, and I just cannot see it happening. One Williams could have a bad day, I suppose, but both of them aren't going to. I don't see Capriati winning Wimbledon, but she is the one player who could hurt them, with Martina Hingis and Lindsay Davenport both absent recuperating from operations.

The Belgians, Justine Henin and Kim Clijsters, have not had the greatest of years, while Monica Seles certainly does not have the game to damage them nowadays. The only other danger is Jelena Dokic, who is in line to face Serena in the quarter-finals.

So it isn't too brave of me to forecast that one of the Williams girls is going to win. The only disappointing thing is that the sister v sister clashes do not produce good matches. Every time they play they rewrite history but you do not look forward to their matches. There has to be lots of nervous energy to make a great match and that just does not exist when they play each other. I don't buy the rumours that their matches are fixed, but all the fist-pumping is certainly an act because the fire isn't there.

Brother and sister clashes over the years have always been like this. When did you ever see a good match between any of the three Maleeva sisters? And in my own family's case, my brother Tony couldn't play me and I couldn't play my other brother, David.

I foresee rather more horses in the men's race, eight instead of three. I divide the eight into two groups of four, with the top group consisting, in no particular order, of Tim Henman, Andre Agassi, Pete Sampras and Roger Federer. Then, in fifth place, I put the top seed, Lleyton Hewitt, with the last three places going to Mark Philippoussis, Greg Rusedski and the official second seed, Marat Safin.

It could well be Henman's year finally to win it because he certainly could not have landed a better draw if he had bribed the Wimbledon committee. His draw is ridiculous, I have never seen one like it in my life. The other seeds in his quarter are clear indication of just how weak grass-court skills are these days. The Australian Open champion, Thomas Johansson, on a good day could possibly bother Tim, but unless Henman chokes, which he has never done at Wimbledon yet, there is no way he can fail to reach the quarter-finals.

In the semi-finals he is seeded to play either Hewitt or Federer, and it is Federer who can do damage here, which is why he is in my top four. He can beat anybody on a given day and if he did face Henman in the semis it would scare me because he could knock off Tim, though doubts remain whether he has the mindset to win seven matches and the title.

Hewitt, as we know, has now beaten Henman five straight times. But if they both play at their peak a good serve-volleyer who can mix it up, like Tim, or Federer for that matter, should beat a counter-puncher like Hewitt seven or eight times out of 10. If it's Hewitt v Henman in the semis, I think Tim will win.

Even though his record this year is appalling, Sampras has a good draw, his class is still there, and if he can produce it for Wimbledon he has a good chance of landing his eighth championship. Is Pete past his peak? Yes, I think he is. But is he still good enough to win if he plays 90 per cent of that peak? Whether he can get to that level is the unknown factor.

Agassi is another aggressive counter-puncher who is playing well and he has a great shot at his second Wimbledon 10 years after his first victory. But he has a tough draw, with Rusedski, Andy Roddick and Philippoussis (whom I have had a bet on at 22-1) in his quarter.

As for Safin, here is a man mountain who should be No 1 in the world. He has too many brain cramps but when he won the US Open in 2000 he was magnificent, so why can't he click at Wimbledon?

John Lloyd was talking to Ronald Atkin