Choice of Champions League second-leg referee for Chelsea semi-final revives 'Barça bias' claim

Conspiracy theorists who share Jose Mourinho's belief that Barcelona's recent success in the Champions League has come with a helping hand from Uefa will feel they have extra ammunition after Erzik Senes, vice-president of Uefa's referees committee, picked fellow Turk Cuneyt Cakir to referee Chelsea's second leg tomorrow night.

Erzik is a former Unicef employee and Mourinho, the Real Madrid coach, famously suggested Barcelona were favoured by Uefa because of their sponsorship of Unicef in a post-match rant last season, after Pepe had been sent off in the Champions League semi-final first leg which Barça won 2-0.

Barcelona renewed their sponsorship of Unicef by signing a one-year deal last May and will carry the organisation's logo on their shirts against Chelsea. Erzik is vice- president of Uefa's referee's committee but also worked as a project manager for Unicef.

Compatriot Cakir – his choice for tomorrow's second leg – has refereed four Champions League games this season and shown no red cards. The 35 year old is also on Uefa's list of match officials for the European Championships this summer.

Last year Mourinho said: "If I say to Uefa what I really think then my career will be finished. As I can't say what I think I will ask the question: Why? I don't understand why? Why [Tom] Ovrebo? Why [Massimo] Busacca? Why [Wolfgang] Stark? Every semi-final the same thing happens. I don't know if it is the publicity of Unicef. My question is why? Why don't they let us play against them? Why send Pepe off? Why not give four penalties in the game against Chelsea. Why send off [Thiago] Motta? Why send off Robin Van Persie? Where does this power come from?"

Meanwhile, Barcelona will have to pick themselves up off the floor after their 2-1 defeat to Real on Saturday virtually guaranteed the Madrid side will win La Liga for the first time since 2008.

Pep Guardiola's Barcelona have never lost three consecutive matches and he was confident his players would find the strength to go again tomorrow night, despite admitting they were too down to talk after the game.

The mood was best summed up by Jorge Valdano, the former Real Madrid director of football: "Nothing tires a team out at this stage of the season quite like a defeat." Barcelona had just lost their second match in three days and relinquished their La Liga crown in the process; with Chelsea on the horizon, no wonder they looked exhausted.

Guardiola said he did not agree that his side's matches against Chelsea and Real Madrid had been "disappointing" but it was hard to find a kinder word for Barça having saved two of their most ineffective performances for the two games that mattered most.

Jose Mourinho's Real only had 27 per cent of the possession, yet they had twice as many shots on goal (six to Barcelona's three), forced three more corners (seven to Barça's four) – and, most importantly, scored twice.

Barça's 2-1 defeat ended a 54-match unbeaten run in the Nou Camp and meant that for only the third time in Guardiola's reign the team had suffered consecutive defeats. They may yet stir from their slumber to overturn Chelsea's first-leg advantage tomorrow night. "If we go through, then everything will be focused on us playing two finals," said Guardiola, whose team have already made it to the Spanish cup final. But the signs were not good on Saturday.

Goalkeeper Victor Valdes flapped at Pepe's header from Angel Di Maria's first-half corner and Carles Puyol was unable to clear the loose ball as Sami Khedira stole in for Madrid's scrappy opener.

Those two, along with Gerard Pique, Eric Abidal and Dani Alves, formed the back five that won the Champions League last season. But with Alves playing up front as Guardiola tinkered, Pique on the bench and unused for the second match running, and Abidal recovering from a liver transplant, the smooth transition from solid defence to attack has gone. The midfield trio of Xavi, Sergio Busquets and Andres Iniesta looked out of sorts. Xavi missed the best chance of the first half, shooting wide after being put through by Lionel Messi, and was taken off for the third match running. "If we could play the game against Chelsea today, then we would," Xavi said yesterday. "We are raging inside to turn the result around. The team is very competitive."

He also dismissed the idea that Barcelona's season is heading for meltdown. "We have managed to win three trophies this season already and we are in the cup final and 90 minutes from the Champions League final. It is within our grasp still to make this a great season," he said.

Xavi's form will need to improve – as will that of Barcelona's misfiring forwards. Last season, Messi was flanked up front by Pedro and David Villa; on Saturday night he had 20-year-old Cristian Tello and the advanced Alves for company. How Guardiola needs Pedro to return to the sort of form that saw everything he touched turn to goal last season, or Villa to return to full fitness.

Without the Spanish national team's top scorer alongside him, Messi has had to battle with what Guardiola described as "two of the best defences in the world" on his own.

Cristiano Ronaldo got the winner on Saturday with his 42nd league goal of the season and now leads Real into Wednesday's second leg with Bayern Munich, who beat Werder Bremen 2-1 at the weekend, but only as Dortmund were confirmed as champions.

Messi has 24 hours less to prepare for the visit of Chelsea. He had 58 touches of the ball on Saturday but failed to get a single shot on target. "We crashed up against a wall," said Busquets, who knows another wall awaits him and his team-mates tomorrow night.