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Barcelona president Josep Maria Bartomeu has made it clear that star player Lionel Messi is not for sale under any circumstances as the Camp Nou outfit look to rebuild after a relatively poor season.

Bartomeu said that Messi is happy at the club and he will be the cornerstone around which the team is built next season, per Marca: "As far as I'm concerned Messi doesn't want to leave. We gave him a new contract not long ago and he's very happy."

Barcelona failed to win any major trophies last season, coming in second in La Liga to Atletico Madrid—while also being knocked out of the Champions League by the same opposition in the quarter-finals—and losing to Real Madrid in the Copa del Rey final.

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As a result, Gerardo Martino departed as manager at the Camp Nou and former player Luis Enrique took up the post, having previously been in charge at Celta Vigo.

Many perceived Barcelona's failure to win anything as a result of a drop in form from Messi himself, with the Champions League loss being put down to a lack of effort on his part, per ESPN's Dermot Corrigan:

However, the criticism seemed somewhat misplaced, as the Argentinian maestro still managed to score bags of goals, per Bleacher Report UK:

He is currently almost single-handedly carrying Argentina through the World Cup in Brazil—he has scored four times in as many matches—and is displaying for all to see why Barcelona would be crazy to ever let him leave the club.

There is certainly a rebuild going on in Barcelona with Cesc Fabregas having already left for Chelsea, Alexis Sanchez reportedly on the way out and an £80 million bid being prepared for Liverpool's Luis Suarez, per Mike Whalley on ESPN FC.

New boss Enrique indicated that changes would be made when he took up the post at the Camp Nou back in May, per Corrigan at ESPN FC:

The players must know that you cannot let a year pass at Barca. If they are not at the level required then there will be changes. We will reinforce the team in the best way possible, to be as competitive as possible. There is a market there -- teams ask a lot of money for players. You must manage it all. We will reinforce, maybe in all lines of the team, to have the best players for the club and for me.

Having already made changes to the attacking unit, Enrique will now likely look to strengthen the back line which was not overly reliable last season.

However, as if it was ever in any doubt, Messi will stay at the Camp Nou for the foreseeable future, and Barca will no doubt soon return to their brilliant best with him running the show.