Lionel Messi has been the undisputed world's best player over the last four years, yet recent performances have seen questions asked.
Perhaps the greatest talent in the reigning Fifa Ballon d'Or winner's locker has been his consistency. Scoring 91 goals in a calender year, as he did in 2012, is impossible without finding the back of the net with regularity. The Argentine is also noted for stepping up his performances on the biggest stage. He has scored in his last two European Cup final appearances.
Yet Barcelona's all-time leading scorer is currently failing to come up to his own other-worldly standards.
His subdued performance in his side's shock 3-1 defeat to Real Madrid at the Nou Camp last night came quick off the heels of his non-existent display in the 2-0 defeat to AC Milan in the Champions League.
The drop in form of Messi was magnified last night by the stellar performance of Cristiano Ronaldo, his only true rival in the 'greatest player' debate. The Real Madrid frontman scored twice and in doing so passed Messi's record to become the first player to score in six straight 'Clasicos' away from home.
Speaking after yesterday's game, Andres Iniesta was forced to come to Messi's defence.
"It is about the team, not about whether Messi is better or worse," said the Spain midfielder.
"We have scored a lot of goals, and so has he in particular. It is just in these two key games we have lacked accuracy and composure. When the team doesn't work well, it is everyone's responsibility."
Messi's achievements have been made possible by the regularity with which he takes to the field. Amid questions over whether he may suffer from burn-out, at the weekend Messi said it suited him to play regularly.
"I am used to playing a lot of games now, and I prefer it this way. I feel better if I don't rest," he told Barca TV.
Yet it appears Messi is suffering. Barcelona announced on their website today that the 25-year-old has been ordered by doctors to stay at home and get some rest. There is a chance he may miss the La Liga meeting against Real Madrid on Saturday.
The statement from Barcelona under the headline 'Unwell Messi misses training' read: "The player was visited at his home this morning by the club’s doctors, who gave him medication and told him to get some rest
"The team will have a day off on Thursday, and the hope is that Messi will be well enough to train on Friday and travel with the team to Madrid"
Their is no doubt that if Messi's form dips, so does that of the team.
While Barcelona appear almost guaranteed the league title with a 12-point gap over second placed Atletico Madrid, two poor performances from Messi and they are now out of the Copa del Rey and facing an uphill task to overturn their Champions League loss to AC Milan.
Messi has scored an incredible 38 goals in the league, netting more goals himself than 16 other teams have individually tallied up in La Liga. While incredible, it could be argued Barca have become too reliant on his goals, with fellow forwards Alexis Sanchez, David Villa and Pedro contributing only 12 between them in the league this term.
In total, Messi has scored 47 goals in 37 matches this term, plus two in the Spanish Super Cup.
The absence of coach Tito Vilanova, who has been missing since the turn of the year after needing a second round of surgery following an operation to remove a tumour from his saliva glands, appears to have affected a team which looks devoid of ideas in the face of an organised and talented defence.
Assistant coach Jordi Roura is in constant contact with Vilanova, but there is little doubt that the tactical knowledge of the head coach has been missed.
"Madrid destroyed Barca in every facet of the game, with an indisputable and overwhelming victory," sports daily Marca wrote today.
"Few teams in history have demonstrated more conviction in a particular style of play (than Barca) but it became clear they lacked confidence in their style of football. Barca played with the ball but didn't play football."
AC Milan visit the Nou Camp for the second leg of their Champions League tie on March 12, and despite the need for Barcelona to find a way through, Iniesta says they will not change their ways.
"We need to get back to the ABC of football, because this is what has helped to make us the team we are," he said.
They also need Messi to get back to what he was.