By John McEnroe
Three-time Wimbledon champion
Of all the last 16 matches on the men's side of the Wimbledon draw, I'm finding Andy Murray against Richard Gasquet the most difficult to call.
This is a huge match for the Frenchman who, let's not forget, was a Wimbledon semi-finalist in 2007 and he needs this match probably as much as, if not more than, Murray.
Gasquet's been struggling - he didn't play the French Open and there have been questions about his heart. He'd love to answer those critics.
"Murray's movement and speed around the court is underrated - it's a big factor towards why he will go far into Grand Slams"
I think it's going to go the distance. As well as Murray has been playing, he's going to have to step it up.
In his third-round victory over Tommy Haas he started out strong and his movement was excellent.
As a matter of fact, I think he intimidated Haas, who looked a little bit sluggish out there.
That helped Murray race to a set and a break up, while his serve was big. As the match got tighter his first serve percentage went down but when he really needed it in the third he picked it up nicely.
The turning point was at 1-1 in the third set when Haas failed to convert a break point and the next game Murray broke and took charge.
Murray's movement and speed around the court is underrated, I don't think people realise how strong he is at 6ft 2in and I think it's a big factor towards why he will go far into Grand Slams.
Gasquet has a tendency to stay deep but, like Haas did with some success as the match progressed, he will look to take advantage of Murray's second serve, which is not as penetrative or as hard as his first - he more or less spins it in.
That's where Gasquet must step in and attack. You also have to stay with Murray mentally because the pressure of being the only British hope seems to be more of an inspiration to him than a problem.
Andy likes the crowd's energy, he handles it well and I think it's going to help him. He has had a good first week and, while you're talking about a considerable step up now, I'd have to go for Murray in five.
606: DEBATE
This guy is so quick and his intensity is so intimidating. Keifer played about as well as he possibly could have and it was a very competitive first set.
Nadal is just so determined to win this tournament. When he won the French Open for the first time he said, 'yeah I feel great about winning the French but I want to win Wimbledon', and that is very impressive.
His serve has got better and better and likewise his willingness to come in to the net. He is so well balanced and moves unbelievably fast. His pace and the spin he generates is phenomenal and, of course, he is so strong.
Look at his physique, then his intensity and then his desire. Combine it with being a lefty, which we don't see very often, and combine that with his talent and work ethic. No wonder he's so hard to beat in a best of five-set match.
The balance of power between Roger Federer and Nadal has become closer. It's clear to me that Rafa has a better chance on grass than Federer has on clay.
I credit Roger for getting to five finals and I picked him again this year as I think he suits these courts slightly better.
But I'll tell you something - the way Nadal's playing right now, it wouldn't surprise me one ounce if he went and won it.
John McEnroe was speaking on BBC Two's Today at Wimbledon.
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