Lionel Messi has scored eight times in nine starts in the league, he has provided four assists and the Barcelona team he leads sit at the top of the table having won 11 and drawn one of their 12 games. It is their best ever start to a league campaign and a fortnight ago they defeated rivals Real Madrid, who now trail by six points. They also won the Spanish Super Copa and in the Champions League Messi has scored four times in two matches and Barcelona lead Group H. No wonder they're so worried about him. Right now, Messi is rubbish. The four-times Ballon d'Or winner is in crisis.

Some crisis. If this is a crisis, it is the kind that most players would love. But Messi is not most players. He made the extraordinary ordinary; now, a victim of the expectations he created, the four-times Ballon d'Or winner is making the very good look, well, not very good. "He set the bar so high that when he doesn't score it feels like it's a problem," says the Barcelona coach, Gerardo "Tata" Martino. "But it's not a problem." The obvious question arises: isn't it? Because if Martino says he is not worried, others are. And not entirely without reason.

Messi hasn't scored in four games. Nothing, you may think. But for the Argentinian, it is the worst run he has endured in two and a half years. Seventeen games into Barcelona's season, he has scored 12 times. At the same point last year it was 21; the year before that it was 20 and the year before that 22. Twelve the year before that, and you have to go back five years to find a season that has started with fewer goals than this one.

Again, there's that bar, set ridiculously high. In the last four seasons Messi has scored a frankly ludicrous amount of goals: 60, 60, 53 and 47. In the calendar year 2012, he scored 91 goals for club and country; with a month and a half left of 2013 he is on 42. That's 42 in 43 games. Still astonishing, just slightly less astonishing. Cristiano Ronaldo, the man against whom he is inevitably compared, has scored 59 in 51.

There's something about Messi, something that's not quite right. Not quite Messi. He appears a fraction slower; he does not react so swiftly or run so quickly. He appears a little distant, not himself; it is legitimate to ask if he fits quite so well in Martino's slightly more direct system, if he will still play such a central role. He didn't score in the clásico, for example, but it was not just that he didn't score that struck spectators. He touched the ball 65 times, according to Sport's analysis; at his best that figure would be closer to 90. Quite simply, he didn't influence the game.

Neymar, the club's summer signing, did. The Brazilian scored one and helped create the other in a 2-1 win. Returning to the right for the first time since Pep Guardiola made a "false No9" of him, distanced from the play, Messi, by contrast, had just one shot on target. He is, said a recent headline in Marca, "playing as a false Messi". The cover of Sport declared: "Objective: get Messi back."

The first step is getting him fit. Messi has suffered three minor injuries already this season and equally worrying is the sensation that this is a continuation of last season, when he came back early from injury to lead Barcelona's defeat of Paris Saint-Germain. Even injured, he had changed everything that night. "He's the best in the world, simple as that," David Beckham said. But Messi was still not right, he couldn't sprint, and the semi-final was a different matter. Messi played but he, like his team-mates, was absent. Barcelona lost 4-0 in Munich.

A player who had largely avoided injuries under Guardiola, re-encountered them and has not thrown them off yet. His first of this new era came during a pre-season that the players considered a shambles. On the opening day of the season, Martino took Messi off after 70 minutes and said he would so again, all the better to protect him. "I'll be careful not to take him off five times in a row," he conceded. Taking Messi off appeared prudent, and he has done so four times, but twice more he suffered muscular injuries, against Atlético and Almería.

Minor issues, but cause for concern. For Messi, especially. Were those injuries now on his mind? Is he holding back? So far this season Messi has missed three games. At this stage last year it was zero; the year before that it was zero and the year before that just one.

Messi returned on 19 October, having missed the last two games for Argentina, but doesn't appear to have reached full speed yet. Javier Mascherano suggested in an interview with El Gráfico that he might be "dosifying" his efforts, aware that the World Cup in Brazil awaits at the end of the season. "What I meant was that he has to think about not getting injured so that he can have more regularity of games," Mascherano explained when the comment caused a stir. "For us he is decisive. We always need him."

The city derby last Friday night brought to a close a week where Barcelona had played three league games in seven days. Messi looked tired; the game was sluggish and so was he. An impressive, dynamic performance in Vigo was overlooked; the two "derbies" either side of it captured the imagination more. "Games against Espanyol are always difficult but it's clear that I am not at 100% yet physically," Messi admitted. "I'm sure that as the games go by I will get back up to speed."

Barcelona next face Milan. It was against the Italians in the spring that Messi produced a superb display, arguably his most recent truly brilliant one, when he scored twice in the first half and led Barcelona to a 4-0 victory. There has been time to rest, to recover, to reset, since the Espanyol match. This clash comes as an obligation but as an opportunity too. "There's always a point in the season that Messi goes a few days without scoring. Maybe he does it to give you lot something to talk about," Dani Alves said at the pre-match press conference. Gerard Piqué added: "Leo will score sooner rather than later. I would love him to score two or three goals every game, but that's impossible."

"Relax," his father, Jorge, insisted. "He'll be back."