Defending against Lionel Messi has proved nigh-on impossible for players down the years.
It's not just the Argentine's speed and unrivalled footwork that makes him so unplayable, but his movement and reading of the game.
From a young age Messi was given the freedom to roam at Barcelona, whereby he would start in a set position but play anywhere across the attacking line.
It was under Pep Guardiola between 2008-2012 where Messi's versatility really came to light as he became the central figure in a revolutionary 'False 9' formation.
Back in 2009, in the build-up to an El Clasico between Real Madrid and Barcelona, Guardiola devised a plan that involved playing without a dedicated centre forward.
Instead, the No.9 would play deeper in between the opposition defence and midfield, therefore adding another option in the middle.
Messi was tasked with the role with Thierry Henry and Samuel Eto'o out wide, and the result was a thumping 6-2 win for Barcelona at the Bernabeu.
Real didn't know what hit them as Messi constantly dropped into the hole to pick up possession and those around him made surging runs forward.
And so the False 9 was born, with Guardiola continuing to use it with Messi, Pedro and David Villa in the years that followed.
One man who knows a bit about playing against Barcelona and Messi in the False 9 is Xabi Alonso, who joined Real in 2009.
In a fascinating collaboration with The Coaches' Voice, Alonso explained and visually demonstrated just how hard it was and how Real eventually stopped it.
Alonso makes it sound so simple, but it would be foolish to think that's the case.
Real quickly discovered that pressing Barcelona's players to win back possession didn't work, so Alonso started man-marking Messi to stop him from receiving possession so easily.News Now - Sport News