Luis Enrique says his last Clasico in charge of Barcelona at Real Madrid on Sunday is a must-win for the reigning La Liga champions.
Anything other than a Barca victory at the Santigao Bernabeu would more or less hand Madrid their first Spanish league title in five years.
Zinedine Zidane's men hold a three-point lead at the top with a game in hand on their rivals.
"Given how close it is to the end of the season it is a decisive weekend," said Enrique on Saturday.
"This time a Clasico can decide or almost decide the league or leave it very open.
"For us it is like a final, only a win will do."
Madrid could be boosted by the return of Gareth Bale from injury, but the fact the Welshman may not be risked is a further sign that Real have far more room for error.
Bale has been sidelined by an inflammation of the muscles around where he suffered ligament damage in his right ankle that kept him out for three months earlier in the season.
"He will be with us tomorrow," said Zidane.
"You will see tomorrow what team we are going to start with."
Should Bale not start, the on-form Isco is favourite to take his place, as he did for Madrid's thrilling 4-2 win over Bayern Munich after extra-time in midweek.
Centre-backs Raphael Varane and Pepe are Madrid's only injury absentees meaning Zidane is expected to name the same starting XI as against Bayern.
"It is another important game. There is a lot of tiredness, but also a lot of excitement and desire to keep doing what we are doing," added the Frenchman.
Barcelona are expected to be without one of their key men despite the club going to extraordinary lengths to try and have Neymar's ban suspended.
The Brazilian is in the midst of a three-game suspension for his red card and subsequent sarcastic applause of the officials in Barca's 2-0 defeat to Malaga two weeks ago.
In an unprecedented move Barca deliberately delayed their final route of appeal to Spain's Court of Arbitration for Sport (TAD) until after the court's normal meeting time on Friday in the hope that would automatically see the ban suspended.
However, even if no ruling from TAD is forthcoming before Sunday, Barca face a legal quagmire as they could be sanctioned with defeat for fielding an ineligible player should Neymar feature.
"As a coach I am prepared to play with Neymar or without him," said Enrique.
Only victory will salvage Barca's season just four days after crashing out of the Champions League at the quarter-final stage to Juventus.
However, Enrique called on his players to embrace that challenge as an extra stimulus rather than be cowered by the pressure at the Bernabeu.
"For some it means it is a very attractive challenge and for others it means pressure," he said.
"I prefer to take it as an attractive and marvellous challenge. It's a chance to move level on points with Madrid."