Wimbledon 2009: Wimbledon legend John McEnroe believes Andy Murray's fitness intimidates his opponents

Murray has won six of his eight career meetings with Federer, including their last four matches, and McEnroe said that the Swiss does not like it one bit.

"The cat-and-mouse style Murray plays is something I like to see. It's a thinking man's game and he has got into Roger's head right now. He's got into Roger's head pretty good recently," McEnroe said.

"Murray's legs are thicker than I've ever seen them, his bounce around the back of the court is impressive, and he's intimidating people with his fitness, which was an issue at the start of his career. His movement is amazing when you think how tall he is. He has got more pop on his serve and he continues to befuddle guys mentally."

When McEnroe was in his prime, no one was ever left under any illusions as to what he was thinking on a tennis court, and it could be argued that the most emotional player on tour now is Federer. McEnroe raged, and Federer cries.

"It was strange to see Federer in tears after he lost the Australian Open final to Nadal," said McEnroe, a winner of three Wimbledon titles, who will be commentating for the BBC at the All England Club this year. "I had an emotional moment with him at Wimbledon last year. I was really surprised to see that happen again in Australia. That shows a vulnerability on Federer's part. In the old days, you wouldn't see that from almost anybody. I think it will bring him some support and show that he's human. That could help him when times get tough.

Still, at least Federer shed some 'happy tears' in Paris this month after winning the French Open for the first time.