FC Barcelona boss Ronald Koeman was left fuming after details regarding Lionel Messi's contract were leaked to the press.

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Messi and Antoine Griezmann fired the Catalans to victory over Athletic Bilbao on Sunday night, taking Barca to second place on the LaLiga table.

However, reports emerged over the weekend detailing the Argentine's contract with the club, and his manager Koeman lashed out at the matter when asked about it in a post-match press conference.

"What came out in the press today was with malicious intent and wanting to do damage to a player that has done so much for Spanish football and for this club," he said, according to Sport.

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"We have to try and find out how Messi's contract's come out in the press. They are things that cannot come out. There are people that want to do us damage.

"If the leak is from within the club, that's very bad. We have to help the players, the coaches to win games. If someone from inside the club has leaked it, they cannot have a future at the club.

"I don't understand why they say he's ruined Barca... He's spent years and years showing his quality as a footballer. We have to highlight what he's done for this club. He's helped make this club great and we have to stop with all this contract nonsense."

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The original report in question came from Spanish publication El Mundo, and Barca have already announced that they are planning to take legal action against them.