Defeat to PSG highlights the defensive issue Barcelona are failing to address

Legend is a term used all too often in the modern world.

But Sergio Busquets is most definitely a legend at Barcelona. A La Masia product, Busquets has been a stalwart of the side since 2008 and has racked up over 600 appearances for the club.

There's no doubt the 32-year old can continue to play an important role in the Barcelona team and at the club generally for the next few years. But in what Ronald Koeman has rightly described as a transitional phase for the famous Catalan club, the holding midfield position Busquets has imperiously dominated for more than a decade has been criminally overlooked in the development and modernisation of the team.

And boy, did Kylian Mbappe and Paris Saint-Germain point it out on Tuesday night.

Quick, fluid and lethal football led to the Parisians thrashing La Blaugrana 4-1 in the first leg of their Champions League round of 16 tie, with Mbappe managing a sublime hat-trick on his first appearance against Barcelona.

For all the clinical finishing that the French star showed during the game, it was in midfield that the match was won and lost. PSG's sharp movement and precise football bypassed Barcelona's defensive lines far too easily and the likes of Marco Verratti, Leandro Paredes and Mbappe himself found space in little pockets which they had absolutely no right to.

Unfortunately, that was partly down to Busquets. As usual, the veteran played as the pivot between defence and more advanced midfield players and, despite doing a solid enough job with the ball, he just couldn't handle his task off it.

Mauricio Pochettino set out a team to score goals and take an advantage back to the French capital - that was clear. Full backs Alessandro Florenzi and Layvin Kurzawa were constantly threatening and found themselves as high up the pitch as they could possibly be, which allowed Mbappe and fellow winger Moise Kean to drift infield and pick up the ball within the width of the penalty area.

This is when it became clear that Busquets didn't have the legs to cope with his opposition alone.

The first goal came through a sweeping team move. Kurzawa found an unmarked Verratti in the Barcelona box after a long diagonal from Marquinhos, before the Italian poked the ball into Mbappe's path, who had moved into the area from deep unopposed with time and space - Busquets had failed to track his run. With space to work with, the PSG forward calmly rounded Clement Lenglet and fired into the roof of the net.

The second was rather unfortunate, as a miscued Gerard Pique clearance landed nicely for Mbappe to smash home. However, had Busquets tracked the Frenchman's run into the box, the outcome may have been different.

Why didn't Koeman just put another defensive midfielder in alongside Busquets to fill the gaps?

Well, to be honest, he couldn't. The Barcelona manager had Miralem Pjanic as a viable option to come on and affect the game in that role, but he once again showed his flakiness while sitting deep and simply couldn't nullify the threat that PSG posed.

The Dutchman replaced Busquets with Pjanic on 78 minutes. Despite providing a larger goal threat than Barcelona's number five, the Bosnian's introduction opened up the game even further and was eventually at fault for PSG's fourth. The big money summer signing went in rashly to try and nick the ball on the edge of the French side's box, but was taken out of the game by Julian Draxler's quick thinking to set up what would turn out to be a devastating counterattack.

In that situation, there's no doubt a player like Busquets would have had a better shot at denying PSG a breakaway. While the Spaniard might have demonstrated his phenomenal ability to read the game, Pjanic showed a lack of composure and recklessness that gifted his opposition a counterattack.

Now, there's no doubt that La Blaugrana have a lot of defensive issues. Against PSG, for example, the full backs were too weak, the forwards and advanced midfielders were lackadaisical in their pressing and the central defenders failed to read the game and track runners at times. But the investment in the likes of Trincao, Ronald Araujo and Pedri and the introduction into the first team of Puig and Ilaix Moriba shows that the club have an eye on the future and the squad's development in those regards.

But Koeman's lack of options in solidifying his deep midfield alongside Busquets - who was clearly being overrun from the outset - shows the process of replacing the 32-year old has been disregarded. It's all well and good to bring in bright, creative starlets but the modernisation and recasting of the gritty and unthanking role of holding midfielder simply has to be a priority in the immediate future for Barcelona.

Otherwise, there's no way La Blaugrana can compete with today's cut-throat and electric-paced elite.