Ronald Koeman said Barcelona "can't aspire to much" without Lionel Messi after the Argentinian scored another landmark goal in Sunday's 2-1 win over Athletic Bilbao.

Messi was headline news earlier in the day when a report by El Mundo claimed the deal he signed at Camp Nou in 2017, which expires at the end of this season, is worth more than €555million.

He proved his worth to Barca with a fine free-kick midway through the first half - his 650th goal for the club - before Jordi Alba's own goal drew Athletic level early in the second half.

Antoine Griezmann secured all three points with the winner 16 minutes from time, though, to help Barca leapfrog Sevilla and Real Madrid into second in LaLiga, 10 points behind leaders Atletico Madrid.

Head coach Koeman was less than impressed with the details of Messi's contract surfacing, but insists the saga did not provide any additional motivation for a player he believes is the world's best.

"We've known, for quite some time, that he's the best in the world," the former Netherlands coach told Movistar Plus.

"He's done a lot for the club. He's decisive during games. You have to respect everything he's done. He's a great player, he gives us creativity in attack. Without Leo, you can't aspire to much."

Koeman added, according to Marca: "He hasn't been more motivated today [because of the reports]. What's happened has been for bad intentions, to cause harm.

"We have to be united and focused. Things that are published have to be put to the side, but it's tough."

It seems unlikely that Barca will rein in Atletico, who can move 13 points clear if they win their game in hand, but Koeman says his improving side have no intention of giving up hope of claiming the title.

"The team is improving," Koeman added. "There's concentration, mentality. I'm not saying we didn't have that before, but we're growing in confidence.

"It's important to be second. We want to be as high as possible. The gap to the leaders is big but we have to keep going."

Griezmann's late winner maintained his superb record against Athletic.

The France international has now been involved in 15 goals against the Basque side (nine goals and six assists), more than he has achieved against any other team in the competition.

The former Atletico Madrid forward was pleased to overcome an obdurate opponent and had words of praise for Ousmane Dembele, whose fine pass played in Oscar Mingueza in the build-up to the winning goal.

Griezmann told Movistar Plus: "Sometimes you play and sometimes you don't but in the end we are all part of this and we need everyone. Ousmane is playing very well, he is taking good care of himself and we try to ensure that he is in the best condition."