Mac puts knife into Davis Cup format

There have been few greater supporters of the Davis Cup than John McEnroe, but the American is not jumping on any bandwagons to criticise players for not representing their country. Andy Murray is among the leading men – a group that includes Roger Federer and Andy Roddick – who have no immediate plans to play in the competition, but McEnroe believes the demands of the schedule make their stance understandable.

"I can see where these guys just bag it," McEnroe said when asked if he thought that Murray had a moral obligation to play in the Davis Cup. "There's as much of a moral obligation to change the format of it as there is on the guys to play in it."

Agreeing that he would not be as committed to the Davis Cup if he was playing today, McEnroe quoted the example of Novak Djokovic, whose recent indifferent form, he believes, is down to his recent hectic schedule.

"It hurt him for six weeks," McEnroe said. "He went straight from Dubai [at the end of February] to Belgrade to play Davis Cup indoors against America and then he went straight to Palm Springs. If you don't think that affected his results at the next couple of events, you're kidding yourself."

McEnroe thinks the International Tennis Federation need to consider options other than the current format (various dates are reserved for the Davis Cup throughout the year), such as playing all the matches in one concentrated period. "I think at the very least I would advocate they don't play Davis Cup in Olympic year – and perhaps it should be played every other year," he said.

"At the absolute bare minimum, which I've been advocating for 30 years, the guys who play in the first week of December in the final should be given an automatic bye. Those two teams shouldn't have to play until June or something. It's absurd they have to come back two months later."

McEnroe, who will be commentating at Wimbledon for the BBC, said the schedule made Federer's fitness record – he has played in 42 Grand Slam tournaments in succession – all the more remarkable, though he wonders how long the Swiss can keep going at such a consistently high level. "I think at some point guys lose an edge, whether you're Roger Federer or not," McEnroe said. "The guy's a human being."

While McEnroe sees Murray, Roddick and Nadal as serious challengers to Federer at Wimbledon, he also made a case for his fellow American John Isner, a 6ft 9in giant with a huge serve who has climbed to No 19 in the world rankings.

"It's not impossible to come up with a scenario where he could win, if the right things come into play," McEnroe said. "No one wants to play a guy like that. I think he's a step above [Ivo] Karlovic. I think he's got more game and he manages a match even better than Karlovic."

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