Real Madrid coach Jose Mourinho was given a ringing endorsement by many of the club's hardcore fans during Sunday's morale-boosting 4-1 comeback win at home to Athletic Bilbao.
As the "Ultras Sur" chanted his name towards the end of the game at the Bernabeu, however, they were drowned out by a significant section of the stadium, whistling the Portuguese for the first time.
Many fans of the nine-times European champions appear to have lost patience with Mourinho following Wednesday's King's Cup quarter-final first leg reverse to Barcelona, which tightened the Spanish and European champions' recent stranglehold over their arch rivals.
An unsourced report in Marca, Spain's biggest-selling sports daily, told of a rift between Mourinho and some of the squad's Spanish internationals.
Pepe's stamp on Lionel Messi's hand during the cup game, which he said was unintentional but which drew widespread condemnation, contributed to a difficult week for the club.
Another report on football chat show Punto Pelota on Sunday night suggested Mourinho, who has said he wants to return to England after his stint at Real, had already decided to leave Madrid in June.
As the cup holders prepare for Wednesday's second leg at the Nou Camp, Real President Florentino Perez may be wondering whether he will live to regret his decision to bet all his chips on Mourinho as he desperately seeks to end Barca's domination and secure an elusive 10th European title.
The construction magnate, who has spent hundreds of millions of euros on players including Cristiano Ronaldo, Kaka and Karim Benzema, was hounded out of the club in 2006 when results did not go his way during his first presidential term.
Perez has repeatedly backed Mourinho, whom he says is the world's best coach, voicing his support even after the Portuguese was caught on camera jabbing a finger into the eye of Barca assistant coach Tito Vilanova and amid accusations Mourinho was damaging Real's image.
Real's players rallied behind their coach after the win against Bilbao, which preserved the La Liga leaders' five-point lead over second-placed Barca with half the season played.
Captain and goalkeeper Iker Casillas told reporters he did not have a bad relationship with anyone and said the dressing room had to pull together if the club were to win trophies.
"The whistles directed at Mourinho are whistles for all of us," Alvaro Arbeloa, another Spain international, added.
If necessary, he would take a holiday in Portugal to prove he had nothing against the Portuguese contingent in the squad, the former Liverpool player joked.
"Mourinho is a great coach, this is an issue for the fans," France striker Benzema said. "We are united and there is nothing else to say."
At his post-match news conference on Sunday, Mourinho refused to answer questions about the Marca report, twice interrupting journalists to insist that he did not read the paper.
Quizzed about the whistling, the former Porto, Chelsea and Inter Milan coach said it was the first time it had happened to him in his career but that it was "not a problem".
"I will continue working and maybe one day I can respond and maybe one day they will be sad," he said.
Barca, meanwhile, are on a high after following up their cup win in Madrid with a 4-1 La Liga success at Malaga.
Lionel Messi grabbed his 15th career hat-trick to take his league tally for the season to 22, one behind Real forward and top scorer Cristiano Ronaldo, who netted two penalties against Bilbao on Sunday.
Should Barca, the 2011 runners-up, eliminate Real, they are likely to face Valencia, who won their first leg at home to Levante 4-1 and play at their city rivals on Thursday.
On the other side of the draw, Bilbao have a 2-0 advantage over Real Mallorca after the Basques won the first leg at the San Mames.
If they can hold on in Mallorca on Wednesday they will play 2006 champions Espanyol or third-tier Mirandes, who are through to the quarters for the first time.
Mirandes stunned Espanyol by opening a two-goal lead in their first leg before the home side struck three times in four minutes late on to secure a 3-2 lead for Tuesday's second leg in Miranda de Ebro.comments