After the leaking of Lionel Messi's salary sent shockwaves through Spain, FC Barcelona manager Ronald Koeman believes the Argentine may have made a decision on his future.

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The contract leak to Spanish publication El Mundo, which many believe came from within the club, is yet another low point in Messi's already troubled relationship with the Catalan giants.

Just when rumours were starting to gain traction that Messi could perhaps stay after all and extend his contract, which is set to expire in June, because he is starting to believe in the new sporting project at Barca, his salary and bonuses were published in a report with a headline suggesting that he is "destroying" the club.

As a consequence, Messi's future at the Camp Nou is once again up in the air, with coach Koeman admitting he is worried the Argentine will leave.

"I'm not confident about that (Messi's future at Barca)," the Dutchman told The Athletic.

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"I'm hopeful, yes, about this because he's still a great player and he's still winning matches for us, for the team.

"I'm enjoying being his coach, if you look at his qualities every day in the training sessions, it's incredible.

"Of course, he came as a young kid to Barcelona. And I still don't see Leo Messi in another shirt other than the Barca shirt.

"I don't have any problems with Leo. He is the captain of the team, I speak to Leo about tactical things and we have a really good professional relationship that I have with all the players."

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Messi is yet to comment on the leaking of his contract details, but responded on the pitch by scoring a superb free-kick in Barca's 2-1 win over Athletic Bilbao on Sunday.