Mo Farah's comments this week have all but ruined two nice and simple media lines.

Firstly, Britain's world and Olympic 5000 and 10,000 metres champion has refrained from committing himself to running in next year's Commonwealth Games in Glasgow, saying it would be "a bonus" if he did it but adding "it is not on my list." Any headlines along the lines of "Glasgow a goer for Mo" will have to wait.

No decision will be taken on involvement at Glasgow 2014, Farah maintains, until he has concluded his main business of the year, namely running his first full marathon in the Virgin London event on April 13. But the multiple gold medallist has gone and spoiled everything by insisting that he will not expect to break the two-hours barrier on his debut over 26.2 miles. What a spoilsport!

Mo Farah has contradicted what he claims are 'crazy' suggestions about him running a sub-two hour marathon on his debut

As Farah explained, the suggestion that he was targeting such an extraordinary landmark - just a month after Kenya's Wilson Kipsang took 19 seconds off the world record in reducing it to 2 hours 03min 23sec at the Berlin Marathon – was "ridiculous", adding: "It's pretty crazy to say that in my first ever marathon I'm going to shave three minutes off.

"If you look at the world record it's slowly been broken before, from 2:04, 2:03. To say I'm going to shave that off is completely crazy.

"I don't think [two hours] is going to be broken in the next 10 years or even beyond that, maybe even 100 years, because if you think about it, it's really difficult."

A totally sensible statement. Farah has every reason to be confident given his achievements in the past couple of years, but he has never been a sportsman given to making dramatic statements of intent. Before setting a startling European 1500m record of 3min 28.81sec in Monaco earlier this year, the man now training in Oregon under the eye of former world marathon record holder Alberto Salazar hazarded only the following:

"I'm really looking forward to it. I have some happy memories of this track so if I can get near 3.33 or under it will be great. But the 1500 is a very different race from the 10k so I will just be hoping to stay in with the guys and see what I can do."

Such was the strength of the story that Farah wanted to produce the 26.2miles equivalent of the Four Minute Mile that Sebastian Coe, and even the man who broke the Four Minute Mile, Sir Roger Bannister, were drawn in to provide comment on it. Coe, with characteristic adroitness, responded that it was "very ambitious", which could have been taken as a measure of polite disbelief. Lord Coe's comments were supplemented by sage words from Sir Roger, who commented: "I don't think Mo will be ready to do it next year but it is of course possible."

Sir Roger Bannister, pictured with a picture of his Four Minute mile achievement in 1954, sagely downplayed the suggestion that Mo Farah was on the brink of another athletics landmark in his first marathon

Farah has now said that the idea that he had it in mind to produce claimed that the theory was coined by his sponsors Nike, who used the term "Sub Two-Hour" for a television show they are making.

Farah, however, has now clarified the genesis of this "highly ambitious" target of his. "The rumours actually started because my sponsors, Nike, are working on a show called 'Sub Two-Hour'," he has said. "They keep working on that, and that's how the rumours started. I never actually said it."

Steve Backley, the former British javelin thrower who won Olympic and world silver as well as European and Commonwealth titles, is one of the most thoughtful characters you will ever find on the subject of sporting ambition and achievement.

Steve Backley, that most thoughtful of sportsmen, believes that many competitors have fallen under the weight of their own predictions

"You do see athletes who talk themselves out of success," he once told me. "They end up putting too much pressure on themselves with predictions, and then find they can't live up to it."

Making a cautious estimation and then surpassing it is surely the course of action for any sportsman or woman. Isn't it? Well, thinking back, I suppose there have been odd examples when the bold approach has paid off. Two words exemplify it supremely: Muhammad Ali.

"I am the greatest. I said that even before I knew I was." Here is the quintessential quote from the all-time heavyweight boxing genius. But there are others which rival it in their glorious rashness – or rash gloriousness:

"If you even dream of beating me you'd better wake up and apologise."

"There's not a man alive who can whup me. I'm too fast. I'm too smart. I'm too pretty. I should be a postage stamp. That's the only way I'll ever get licked."

Muhammad Ali makes one of his predictions in 1963 - Henry Cooper will fall in round five

Perhaps Ali's take on golf stands as his boldest of statements: "I'm the best. I just haven't played yet."

In a more serious vein, Ali attempted to explain the philosophy of his approach: "It's a repetition of affirmations that leads to belief. And once that belief becomes deep conviction, things begin to happen. "

In more recent times, predictions of success from Usain Bolt have matched those of Ali in their airy certainty, if not their colourful garb. Here is another protagonist from the School of Bold Predictions.

But for every sporting figure who lives up to his or her own hype, there is another who falls under it. I will never forget, for instance, Dave Bedford's invitation to the Great British Public before the 1972 Munich Olympics - issued exclusively in The Sun - to "stand by your beds and watch me win a gold medal for Britain" presaged a sadly predictable turn of events as he finished sixth in the 10,000m final.

A bitterly disappointing turn of events - and one which, I am ashamed to say, provoked me to land a blow on my younger brother after he made what I deemed to be a dismissive comment after we had both watched the race on TV. Verily, the bold sporting prediction is a double-edged sword. And Mo does well to avoid it.

Mike Rowbottom, one of Britain's most talented sportswriters, covered the London 2012 Olympics and Paralympics as chief feature writer for insidethegames, having covered the previous five summer Games, and four winter Games, for The Independent. He has worked for the Daily Mail, The Times, The Observer, The Sunday Correspondent and The Guardian. His latest book Foul Play – the Dark Arts of Cheating in Sport (Bloomsbury £12.99) is available at the insidethegames.biz shop. To follow him on Twitter click here.