Lionel Messi
Messi has not scored in his last four games in pursuit of his 500th career goalGetty Images

Barcelona and Leo Messi have undergone a Jekyll-and-Hyde transformation in the last three weeks. It all started at Villarreal; Barca were leading the table by eight points and marching to the title with the Argentina international as standard-bearer. Then they drew against the so-called Yellow Submarine, lost El Clasico against Real Madrid and, for the seventh consecutive visit, were unable to win at Real Sociedad, losing 1-0. All this left Atletico Madrid just three points behind them at La Liga summit, with six games remaining.

Just a month ago, Barcelona were thinking about becoming the first team to retain the Champions League. But now they are frantic with worry. Diego Simeone's Atletico could knock the Catalans out at the quarter-final stage on Wednesday (13 April) in a repeat of two years ago when they ended their record of six consecutive semi-final appearances.

It is not all doom and gloom for Barcelona, however. Luis Enrique's side still lead the table; they play Sevilla in the Spanish Cup final in May and won the first leg of their last-eight tie against Atlético 2-1, albeit somewhat unconvincingly having played most of the match against 10 men following Fernando Torres's red card. But failure is nevertheless a realistic possibility, largely due to Messi's worst scoring streak in five years

The defeat at Sociedad means Messi has not scored or provided an assist in four games. Not since April 2010 has the five-time world footballer of the year failed to contribute to a goal in four straight matches. And the run has coincided with Barcelona dropping eight points in three league games for the first time since May 2009. It is surely no coincidence, but more importantly, are there any signs of recovery from Barca's number 10?

After the first leg against Atletico, in which he looked uncharacteristically sluggish, Messi took advantage of the day off Enrique gave the squad to travel to Italy to visit his dietitian Giuliano Poser. The famous doctor has taken charge of Messi's nutrition for the last few years, helping him stay in the best shape of his career. However, his treatment had no impact on Messi's performance in San Sebastian. He looked lost against Sociedad; his body language was striking as he was unable to put pressure on Basque defenders. He was not the unstoppable player who can change the course of events.

Curiously, this recent loss of form has come with Messi in search of his 500th goal as a professional. A milestone which was expected to be a formality has become a curse. Barcelona face two challenges this week in the form of Atletico in the Champions League and the La Liga visit of Valencia on Sunday (17 April). Two further setbacks could see their season fall to pieces.

"It is a marvellous opportunity to show we are the best team in the world and that is why we carry that badge on our chest. Pessimistic thoughts and opinions that I am sure will accompany us in the coming days do not benefit the team at all," Enrique told National. It all depends on Messi. If he returns to peak form, the media will find themselves quoting James Callaghan and Supertramp. Crisis? What crisis?