Formula 1 experts have been musing about just where it has all gone wrong for world championship leader Jenson Button of late, as the Brawn GP star has seen his dominance of proceedings in 2009 come under fire from three fronts as the season closes in.

Having triumphed in six of the opening seven grands prix of the campaign, Button rapidly marked himself out as favourite for title glory this year, but in the past four encounters he has finished no higher than fifth and notched up only eleven points. By contrast, his challengers for the crown - team-mate Rubens Barrichello and Red Bull Racing duo Mark Webber and Sebastian Vettel - have all won at least once and tallied respectively 19, 24 and 18 points over the same four-race period. So, where has it all gone so wrong?

"I'm not sure whether something has changed psychologically for Button since Turkey," wrote friend, 13-time grand prix-winner and now BBC F1 pundit David Coulthard in his column for the Daily Telegraph. "Perhaps he has developed something akin to the yips in golf, but he is certainly not the fluent force of the early season."

"Button is tightening up in the car," concurred fellow ex-grand prix ace and BBC commentator Martin Brundle. "Can he lose the championship from here? Of course he can."

At Silverstone, the N?rburgring and the Hungaroring, Button could point to the fact that his Brawn GP BGP 001 - undoubtedly the form machine of the early part of the season - had been overtaken by the Red Bull RB5 and a number of other competitors in terms of out-and-out speed.

However, with the car right back on the pace again in Valencia last weekend - witness Barrichello's commanding victory - the Briton has acknowledged that he must look within to find the improvements he needs, admitting he has to 'get his ar*e together' if he is not to risk throwing the ultimate trophy away [see separate story - click here]. And fast.

"This was the first time when we have had a strong car that I have not been able to get the most out of," the 29-year-old confessed of his European Grand Prix performance, speaking to The Sun. "I am going to go to Spa and be more aggressive, for sure. The team have asked me to push harder now if I want to win the title."

"The problem must be something within Jenson," concurred former three-time F1 World Champion Niki Lauda, speaking to the Daily Mirror. "Something must have gone wrong in his own mind. He must find the solution within himself, and I think he will."