Lionel Messi may well be recognised as the world's greatest player, but it's safe to say that he is enduring a tricky period in his career right now.
Indeed, it has been well and truly highlighted that he's failing to produce the goods; for the first time in his career, he has gone five straight games without scoring or assisting a goal for Barcelona.
What is going on? Of course, every player has a blip, but we just never expected Messi to have one. Let's be honest, it probably won't be too long before he proves his class once again, but, right now, something isn't quite right.
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As Barcelona crashed out of the Champions League at the hands of Atletico Madrid on Wednesday night, Messi failed to stamp his mark on proceedings. Ultimately, he just couldn't get into the game as Diego Simeone's side defended admirably.
So what's his problem? Well, we may have an answer. According to Spanish outlet AS, the versatile superstar only ran seven kilometres against Atletico - less than any other player.
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Messi's Barcelona teammates certainly ran a great deal further; the likes of Jordi Alba, Sergio Busquets and Andres Iniesta all ran over 10k. Ultimately, Barca ran 102 kilometers during the showdown and Messi only contributed seven of them.
Atletico stars were also streets ahead of Messi; the likes of Koke (12.2km), Saul (12.1km), Gabi (11.8km) and Antoine Griezmann (11.4km) all record impressive statistics. For one reason or another, Messi isn't running the required amount.
Balague has his say
Sky Sports pundit Guillem Balgaue has insisted that the notion Messi is struggling with muscle problems could be true.
Balague told Sky Sports News HQ: "He has not scored in five games, and Barcelona depend on a very good Messi.
"There's two ways to explain this. First, you look at him and he's dropping deeper, he's walking instead of running - although he normally does that - and he doesn't look as sharp.
"When he doesn't feel sharp he doesn't get in the box. As a midfielder, he's good but he's not that great.
"But you can also explain it in a different way. Minutes after the Atletico Madrid game finished a story came out that he has been struggling with muscle problems.
"Not an injury as such, but about three weeks ago he went to Venice to see a nutritionist and he was asking him, 'Why is it I don't feel well at the moment?'
"It could be the training and he's in pain certainly, and all those things have made him perform at a lesser level.
"Some will say it's just excuses, but look back at his last five games and you can see it hasn't been the same Messi. I've checked with the family and the muscle issues are one of the problems that is worrying him."
What do you think is wrong with Messi? Have your say below!