Xavi Hernandez says a win for Barcelona over eternal rivals Real Madrid on Sunday would be a morale boost, but would not end the Liga title race.
Barca would stretch their Primera Division lead to 11 points with a victory, but the Catalan midfielder said October was too early for anyone to declare that the title had been decided.
"They are three very important points, but the Clasico will not decide the league," Xavi, 32, said. "This has only just begun. It is early to draw conclusions - but yes, it would be important.
"It is a big opportunity, and the objective is to increase the advantage. Beating our eternal rival would boost morale and confidence. Even still, La Liga will not be over. Whatever happens, there is still a long way to go."
Barca coach Tito Vilanova's major selection headache for the game is in defence, with Carles Puyol definitely out after dislocating his elbow at Benfica on Tuesday, Gerard Pique still hoping to recover from an ankle knock and Alex Song still learning the blaugrana system following his summer move from Arsenal.
"[Pique] is trying," Xavi said. "He has not trained for ten days. Everyone wants to play, and tomorrow he will know. Puyol was very unfortunate. He is our captain and a big loss. Song has played a few games at centre-back and he can do it perfectly well."
Madrid boss Jose Mourinho has tried different ways to get the better of Barca in their recent meetings, with Real often looking to impose their greater athleticism and physical power.
Xavi said he expected another tough challenge on Sunday, whichever tactical system Mourinho chose. "Madrid have changed their system various times," he said.
"Sometimes they play with a trivote [three defensive midfielders], sometimes with two and a mediapunta [attacking midfielder]. They always have punch, they are very strong physically, can take the game at a set piece. They are powerful, as always."
The Masia academy graduate confirmed recent media stories that his agent was speaking to the club about a new contract which would see him spend his entire career there.
"I am very happy with my career and proud of being here so many years, at a demanding club," he said. "You look back and there are great moments, others not so much, but they made me learn.
"This is my club - the best in the world - and I would like to retire here. My agent is speaking with the club. They are happy with me, and I do not believe there will be a problem."
Recent calls within Catalonia for secession from Spain have led to a heightened political atmosphere ahead of the game, at which Barcelona will give all 98,000 spectators coloured pieces of cardboard to hold up before kick-off so the entire stadium can be decked with the red and yellow colours of the Catalan flag.
Xavi said this made sense to him as Barca was a symbol of Catalonia, but stressed that he and his team-mates would concentrate on making their fans happy by winning the game.
"It seems good to me, logical, normal," he said. "We are Barcelona, we represent Catalonia and we are with whatever the Catalans want. We try and keep away from non-sporting things. We know the political theme is there, that people have the right to express themselves as they believe, but we are here to play football."