Nick Bollettieri: Lack of self-belief means Henman will never be champion

First things first. I don't think Tim Henman can win Wimbledon. The issue is not whether he has the tools for the job. He has them. He's one of the best players on grass, his forehand has improved tremendously and he's worked on his backhand. But I don't believe that Tim believes, deep in his heart, that he can do it. I don't know if he's ever had that belief.

I'm not questioning Tim's ability to compete deep into the second week. I'm so respectful of him and I'd be happy for him to prove me wrong. But does he have that essential belief in himself that makes the difference between a Grand Slam winner and somebody who nearly gets there? Personally, I don't think so.

So who is going to win the men's singles? It's tough to pick a clear winner. There's nobody out there like Pete Sampras, scary and dominating and respected who you could confidently predict will win. There is Andre Agassi but Andre has to grind his way to victory if he's going to do it. I'm not discounting him, he has a chance, but as much as I want Andre to win, it gets harder as you get older.

There are a bunch of other contenders. Lleyton Hewitt has something to prove. They say champions are always champions but he must perform on the court when it matters. Splitting up with his coach, Jason Stoltenberg, won't worry him. Hewitt doesn't care what people think and he has attitude. The drawback is that I don't think people are frightened of him any more. He needs to start knocking some heads again if he's going to do it.

Andy Roddick is going to be interesting. His coach, Brad Gilbert, has a knack of getting guys to win. He proved that with Andre.

There are some big servers who will be dangerous to whoever meets them. Mark Philippoussis is capable of going all the way. Fernando Gonzalez can blast opponents away. Greg Rusedski also has a big serve and no one would be happy to play him if he's on form. Rusedski can also possess a bit of an edge, let's call it attitude.

So those guys have different claims but you cannot discount others. Could one of the group of Argentinians come through? It's quite possible. And in my opinion, it's just as likely as Roger Federer doing anything. He just hasn't shown yet that he can really step up.

In the women's singles, I can predict more confidently. I'm going for a Williams sisters final with Venus winning. This is a big, big tournament for Venus, a chance for her to get back towards where she was. Serena can be beaten, we saw that in Paris. And Wimbledon is really special to Venus. She wants it. My only reservation with Venus is her groin problem, especially if she slides on the grass. But if she's fit, I think we'll have that final and that outcome.

Of the other women contenders, Justine Henin-Hardenne has a game that's good on grass. She's going to come into the tournament full of confidence after winning at Roland Garros but there's a question over injuries, I think.

Kim Clijsters is going to be darn mad, in fact furious because of her lack of performance in the final of the French Open. She couldn't hit a ball or move her feet. That display will fill her with the pow and bang at Wimbledon to go well into the second week but I don't see her in the final.

Nick Bollettieri, who will be writing in The Independent throughout the championships, is the president and founder of the Nick Bollettieri Tennis Academy in Florida and has coached many of the world's leading players over the last five decades