Pep Guardiola prepares to take on Jose Mourinho tonight in what will be their 11th meeting in 18 months. It is as difficult to call as any of the 10 previous clasicos, a far safer bet might be banking on it being their last.
They could go a 12th round on 19 May in Munich in the Champions League final, but disappointing semi-final first-leg results for Barcelona and Real Madrid have made that far less likely, and less probable still, is that both coaches will agree to stay put for another season.
Guardiola is now refusing even to answer questions on the subject of renewing his current deal that runs out at the end of June. "I don't have good memories of the Madrid-Barça games – neither the victories nor the defeats – there were always other things that took away from the football. Good luck to the referee," he said last night, adding that he had not thought about whether this game at the Nou Camp would be his last confrontation with Mourinho.
With soundbites such as "I never said, I wanted to leave" and "I have two years left on my contract", Mourinho has retreated from the stance adopted at the start of the year when his exit looked certain but his options remain open. His decision will depend on honours accumulated, offers on the table, and – if things go wrong between now and the end of the season – the opinions of his employers. Guardiola's choice seems far less straightforward.
The Barcelona coach told the club's sporting director, Andoni Zubizarreta, last November that he did not feel he had the physical and mental strength for another season. The doubts were expressed as his assistant, Tito Vilanova, had emergency surgery to remove a tumour in his throat.
He has returned to work but those close to Guardiola and his No 2 suggest ongoing concerns about the need for Vilanova to reduce his workload and the Barcelona coach's lack of appetite to continue without his trusted assistant are in part behind his unwillingness to commit.
The club captain, Xavi Hernandez, said this week: "We don't talk about it in the dressing room. We want him to continue, but it is up to him."
Guardiola has also been strained by the intensity of his incredible first four years at the club. "If we reach the Champions League final we will have played every possible match in three of the four seasons" he said ahead of this week's semi-final first leg.
It seems most likely that he would take a year out, not accepting any of the offers that have already reached his agent, Josep Maria Orobitg, if he decides to leave. The current Athletic Bilbao coach, Marcelo Bielsa, and former Barcelona player Ernesto Valverde, who has just quit Olympiakos after winning his third Greek Super League, are options.
His players are the only ones who can convince him to continue, say those who believe Guardiola is currently closer to walking than staying. They can start by winning tonight to take them to within one point of Real, who led La Liga by 10 points a month ago.
"If we win it will give us a boost ahead of the Chelsea game but if we don't get the result then these players are capable of picking themselves up for a different competition," he said. Asked if he felt frustrated by the defeat at Stamford Bridge he added: "It is wrong to use the word frustrating. When one team puts 11 players in the box, 11! Drogba was in the box too, it is not simple. With all that defence it was impressive that we created so many chances."