John McEnroe believes Andy Murray will break into the top 20 in the world before next year's Wimbledon - and then gatecrash the top ten.

Fourteen months ago, three- times Wimbledon champion McEnroe crushed the Scottish teenage prospect 6-1 in their Superset knockout match at Wembley Arena.

Eighteen-year-old Murray has made huge strides since then, shooting up to 64th in the world, but 46-year-old McEnroe is not in the least surprised.

"He seemed like someone who was going to learn fast," McEnroe said. "He's got guile, he keeps people off-balance and he's grown."

McEnroe added: "Andy is going to be one of the top guys in the world. He's going to be a top-ten player, most likely. He'll probably be in the top 20 by Wimbledon.

"It's nice but being No 64 in the world isn't going to put him on the Wheaties box, or whatever your favourite cereal is here, so he's going to have to make progress and I suggest he will.

"I went from 233 to 71 in one tournament at Wimbledon, Mats Wilander at 17 won the French and Michael Chang did it at 17 or 18. If you want to compare with those type of players, he's gooing to have to take a step up.

"I think he can do it. I think he'll break into the top 20 but I'm not quite sure how high he can go. He's had some issues physically."

He also backed Murray after the youngster sparked controversy this week when he hit out over the Lawn Tennis Association's perceived treatment of his older brother Jamie.

The hot prospect claimed the LTA had "ruined" his brother by trying to re-model his forehand when he attended a residential training centre in Cambridgeshire as a 12-year-old.

McEnroe, never one to shy away from controversy, believes the youngster was right to speak out.

He added: "I'm all for it, absolutely - you're asking the wrong person if you expect me to say no. I don't know the facts but it's good to see Andy stick up for his brother."

But McEnroe reflected: "There's always 'why aren't they doing more' with both the US Tennis Association and the LTA. This has been going on 20 or 30 years, ever since I started coming here.

"There was a discussion that I was going to be involved with the LTA but that hasn't panned out; why, I'm not quite sure."

McEnroe, who shook off an attack of flu to play in this week's Master Tennis at London's Royal Albert Hall, was speaking before a match against Sweden's Mikael Pernfors

Pat Cash took the deciding champions tie-break to beat Frenchman Cedric Pioline 3-6 6-3 10-7 in their final group match - but both players had already qualified for today's quarter-finals.