Real Madrid have one hand on a first La Liga trophy in four years after Cristiano Ronaldo scored a brilliant winner in a 2-1 victory at Barcelona on Saturday that stretched their lead over their bitter rivals to seven points with four games left.
On a dramatic, rain-lashed night at the Nou Camp, the Portuguese forward's 73rd-minute strike from Mesut Ozil's superb assist secured the win his coach and compatriot Jose Mourinho had sought in vain in eight previous trips to Barca's imposing arena during his otherwise glittering career.
It was Real's first success in eight La Liga 'Clasicos' -- four of them before Mourinho arrived from Inter Milan -- and gives them a timely boost for Wednesday's Champions League semi-final second leg at home to Bayern Munich, when they will seek to overturn a 2-1 deficit.
"We have struck a very significant blow but it's not yet decisive," Real midfielder Xabi Alonso said in an interview with Spanish television.
"Of course it's an important step towards the title but now we have to see it home," added the Spain international.
"Cristiano's goal, coming straight after they levelled, broke their stride and that was fundamental.
"We controlled the match perfectly. It was a great performance, a fantastic result and I am very happy. Now we have another key match on Wednesday."
Barca, by contrast, need to regroup after suffering back-to-back defeats for the first time in almost three years following Saturday's reverse and a 1-0 loss at Chelsea in their Champions League semi-final first leg on Wednesday.
Pep Guardiola, whose only defeat in 14 previous 'Clasicos' as Barca coach was in last year's King's Cup final, may also have his tactics questioned after he left Alexis Sanchez, Cesc Fabregas and Pedro out of his starting line-up.
Sanchez came off the bench to snatch a 70th-minute equaliser after a rare Sami Khedira goal had given Real an early lead, while a toothless Barca could have done with Fabregas's creativity and eye for goal much earlier than the 80th minute.
Guardiola opened his news conference by conceding his bid to lead Barca to a fourth straight La Liga crown had failed.
"I congratulate Real Madrid on their victory and on the league title," the former Barca and Spain midfielder said.
"Right now the players are tired and sad and I can't say if there will be a psychological effect for the Chelsea game," he added.
"We will try to find a way to attack Chelsea but now we have to rest and recover and try to forget tonight's game as quickly as possible."