The Champion is on the ropes and it is the former corner man who could deliver the knockout blow. They don't refer to Jose Mourinho "The Special One" in Barcelona but rather "The Translator". Tonight, though, the club's former interpreter could eliminate the European Cup holders from the tournament one game short of the end of the group stages.
If Rubin Kazan beat Dynamo Kiev in a game that will already have finished before Internazionale and Barcelona kick off at the Nou Camp, the Spaniards will go out if they lose – left to scrap for a Europa League place in the final round of Group F matches.
Barcelona's coach, Pep Guardiola, was typically nonchalant ahead of such a premature season-decider. "The result of the other game will not affect us at all," he said. "Even if we hear that Rubin are winning and we are losing and going out, then we will go out attacking, playing the only way we know how."
Not to be outdone in the nonchalance stakes, Mourinho said the fitness of Barça's star player, Lionel Messi, would not affect his plans. "If Messi plays then I will play [Cristian] Chivu, if Pedro plays then I will play Chivu, if [Andres] Iniesta plays then I will play Chivu. My defence does not change. My only doubt is if [Wesley] Sneijder will be fit or not," said the Inter coach, who admitted that beating Barcelona always gave extra satisfaction.
"I come back to Barcelona with only gratitude for all the experience that they gave me in my formation as a coach. But I have played six games against them with Chelsea and also with Inter and they have been emotional games. I have a debt to the club but with all my soul I am determined to beat them every time."
Labelling them the best side in the world, he added: "I prefer to play a game that is going to be very difficult than a game that is going to be too easy for us. A Chelsea v Liverpool for me is better than a Chelsea v Birmingham – those games worry me more when there is a question about getting the players motivated.
"The odds on Barça winning the Champions League have not changed. They were the favourites before and they are still the favourites. They are the best team in Europe and the champions, but anything can happen. It could be that Kiev and Rubin go through to the next round and Inter and Barça are left to fight it out for the Uefa Cup spot."
Barça have experienced a slight wobble domestically, which means they will go into Sunday's clasico a point behind Real Madrid. There is a sense that they are being found out this season. At the weekend, Athletic Bilbao swamped the midfield and stopped both Dani Alves and Gerard Pique from striding out with the ball from the back. Easier said than done, but a team of Inter's calibre will be capable of similar smothering tactics, and the defender Carles Puyol is aware that, while their form might not have affected the odds on them regaining their European crown, their gleam of invincibility has dulled somewhat.
He admitted: "The rivals know us better now. We have no doubts about the way we are playing and we know what we have to do in this game. We did it throughout last season – win football matches." Although he added with caution: "We all have the same desire as last year – the results will either accompany that or not. We are just missing out on some luck. Last year everything went in for us."
Everything going in last season had a lot to do with the then Barça striker Samuel Eto'o being in spectacular form. Tonight he will be wearing the blue and black of Internazionale. The Cameroon forward has already said he would not celebrate were he to score, and the man who decided it was time the club sold him, coach Guardiola, said he believed the fans would give him the reception he deserved.
Eto'o will partner the in-form Diego Milito for Inter. Barcelona will make a decision on their strikers as late as possible. Guardiola refused to rule out Messi starting while admitting his missing out would be a massive loss in what is Barcelona's biggest game since May's European Cup final.
He said: "Messi is the best player in the world, of course we will miss him if he does not play. If [Michael] Jordan doesn't play for the Chicago Bulls then they miss him, if Kobe [Bryant] doesn't play for the Lakers they miss him, but we have to play with what we have."
One man who should be 100 per cent is Thierry Henry, and Guardiola admitted he has a big part to play. "He knows what an important game this is. He is crazy about going all the way again in this competition and he will be fully focused."
Crunch time: Four who must step up at Nou Camp
Just one goal for Barcelona since last May and a handful of under-par displays have angered supporters. It's time for the Frenchman to deliver and what better moment, as his handball against Ireland is threatening to be the only thing he is remembered for outside of north London.
It was Eto'o's knack of scoring goals in big games that made him so important for Barcelona. It has been tougher for him at Inter, where Italian defences have allowed him less space and there is no Messi to help him, but in the wide open spaces of the Nou Camp he will be more at home.
The Swede has not scored in a knockout match in the Champions League and, although this is a group game, it's a group game of knockout proportions. Has as much to prove to Inter fans as Eto'o has to Barça supporters.
The Argentine is currently being overlooked for a World Cup place. The big striker has struck up a rapport with Eto'o and will look to hurt Barça in the air.