Zlatan Ibrahimovic's return to Barcelona ended with the Swede feeling "disgusted" after two Lionel Messi penalties led to AC Milan's 3-1 loss and exit from the Champions League.
Ibrahimovic was back at Camp Nou for the first time since his 2010 departure from the Spanish champions, after just one season, and while the striker set up the Italian club's lone goal from Antonio Nocerino, he was prevented from scoring.
After the final whistle, Ibrahimovic echoed former Inter Milan and current Real Madrid coach Jose Mourinho's belief that Barca's European success has been helped by match officials following a disputed penalty decision.
"I'm just disgusted," the Sweden international said. "They are the best team in the world but at 1-1 and, playing with intelligence, you can do something. (But) I understand better why Mourinho gets upset every time he plays here - in my opinion it was not fair."
Mourinho was handed a ban last season, following defeat to Barcelona, when he accused Uefa of aiding the Catalan club towards their European Cup title in 2009.
Milan's players were left aggrieved when Dutch referee Bjorn Kuipers booked Alessandro Nesta in the 40th minute for yanking down Sergio Busquets inside the area, as the pair tussled during a corner kick. It was the kind of shirt pulling that often goes unpunished in top games, and started well before the corner had been taken.
Messi stepped up to score his second spot kick of the match to put the hosts back in front, before Andres Iniesta's second-half goal sealed the win.
"The ball wasn't in play and he called it. It was weird, odd, it ruined the game," Ibrahimovic said. "I still don't understand what he whistled. If he calls those he should call the others. Without him the game would have been 50-50."
Barca eliminated Arsenal last season in the quarter-finals after Robin van Persie was given a second booking for continuing to play after the whistle had gone early in the second half, with the game tied 1-1.
In the semi-finals, Real were left with 10 men for most of the second half of their 2-0, first-leg defeat when Pepe was red carded, which led to Mourinho's criticism.
"Sometimes the referee made too many concessions," Milan coach Massimiliano Allegri said. "I don't know if it proved decisive. We made a mistake on the first penalty but he helped on the second. Playing Barca is never easy."
Barcelona coach Pep Guardiola offered few apologies after leading his team into the Champions League last four for a record fifth straight season. Only Real Madrid have achieved such a feat in the history of the European Cup, on their way to a record five straight triumphs between 1956-60.
"You can talk all you want about referees but that makes it five straight semi-finals, the fruits of our talent and a lot of work," Guardiola said.
Apart from the penalty, Ibrahimovic - who played one season for Mourinho at Inter - did not leave with an entirely sour taste in his mouth.
"It was a good experience, we lost the game 3-1 playing against the best team in the world," said Ibrahimovic, who joined Barcelona from Inter in 2009 in a swap that included striker Samuel Eto'o.
"We were there until the second penalty, and this we have to discuss."
