"This isn't something that necessarily is going to stay with him but it's a concern. If you've turned your ankle five times in two years, that's a worry.
"His talent's there, but he's still green. He's lanky but you look at certain guys and they just know how to play.
"He's one of those guys that, to me, was born to be a tennis player. Now he's got to take advantage of that talent."
How Murray advances will depend to a great extent on how he is coached after Wimbledon.
The Lawn Tennis Association's head of men's training, Mark Petchey, is helping out but a more permanent arrangement will need to be worked out.
Three-times Wimbledon champion McEnroe hoped he would have been able to help Murray over the last couple of years but an agreement with the LTA to occasionally hit with Britain's best youngsters has not worked out.
Meanwhile, Elena Baltacha was playing 1994 Wimbledon champion Conchita Martinez at Eastbourne today.
The British No1 is the only home player left in the Hastings Direct event after No2 Amanda Janes lost her first round match to Nathalie Dechy, of France, 6-1, 6-1.
