When Fernando Torres put Atletico Madrid 1-0 up against Barcelona earlier this season, Diego Simeone failed to celebrate. Why?
Well, rumour has it that Simeone was about to celebrate until he saw Lionel Messi wander off the substitutes bench and begin warming up. If you think Simeone was being a tad melodramatic, bear in mind that Messi subsequently came on and Barcelona won 2-1.
That turnaround sums up Messi at Barcelona - the saviour to all their problems. It's unclear whether Barcelona's reliance on Messi reflects their weakness as a team or Messi's greatness, though.
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It's remarkable how one player, no matter how great, can influence an already outstanding team so heavily.
The Catalonians are a side saturated in world-class talent, so how can they struggle so much without their talisman? They needed two late goals to see off Bayer Leverkusen in the Champions League on Tuesday - the last time the teams met at the Camp Nou, Barca won 7-1 and Messi scored five.
Cast your minds back to the 2012/13 season and Barca's run to the Champions League semi-finals, where Messi struggled for fitness. In the quarter-finals against PSG, the Catalans went 1-0 down - cue the arrival of Messi. Of course, they went through.
In the semi-finals, they got steamrolled by Bayern - the odds were stacked against them after a 4-0 first leg defeat. Such is Barcelona's ability, however, some naive hopefuls still tipped them to progress after the second leg.
After they found out Messi wasn't starting, though, even the most optimistic Barca fan has lost hope.
Perhaps the reason for their struggles without Messi is the demands the Argentinian places on the team. Messi wants the ball all the time. No matter what position he's in or how much pressure he's under, Messi will demand the ball - and more often than not he'll get it.
When the Argentine is playing, the tactic of getting him the ball is a fine one - it's when he's not playing that it all starts to unravel. If all your attacks go through one man, it creates confusion when he's not there.
Who's going to get on the ball from deep? Who's going to make the incisive dribbles? Who's going to score and create the goals? Even the best players can become lost without their leader. Without Messi, Barca are like a Rolls Royce without the engine.
If there is a solution to the problem of playing without Messi, Barcelona won't realise it. They can adapt their tactics as much as they want, but when Messi returns, he will demand the ball and his teammates will give it to him.
When you have the best player of all time playing in your team it's hard to ignore him, especially when he's bailed Barcelona out as many times as Messi has.