Paris Saint-Germain boss Unai Emery was left frustrated with the referee after his side threw away a lead to lose 3-1 to Real Madrid on Wednesday.
Adrien Rabiot gave the visitors the lead at the Santiago Bernabeu before a Cristiano Ronaldo double and a strike from Marcelo earned the Champions League holders a first-leg advantage in their last-16 tie.
Ronaldo's first goal, his 100th in the competition for Madrid, came from the penalty spot after referee Gianluca Rocchi penalised Giovani Lo Celso for pulling back Toni Kroos inside the area.
Madrid survived a scare of their own in the second half when the ball struck the upper arm of captain Sergio Ramos in the area, and Emery felt his side were not given fair treatment by the officials.
"I have conflicting feelings," he told a news conference. "The 1-1 strengthened them after a very debatable decision by the referee. The small details didn't help us.
"After that, we were better with the ball and when we had control we always had the ambition to score a second goal.
"A debatable referee call opened the possibility of a comeback. And with that encouragement [after their second goal], they made it 3-1.
Great win in front of the home fans! Still a lot of work to be done but onto the second leg to finish the job pic.twitter.com/ubZe5M0xPX-- Gareth Bale (@GarethBale11) February 14, 2018
"I've been told there could have been a handball by Ramos. I didn't see it but they suggested it was.
"If you give the first one, the second one is, too. It's your job and if it's a penalty, you have to blow for it.
"It's not a question of justification. I think we could have come back if the refereeing decisions don't go the other way."
Despite the unfavourable result, Emery insists he was happy with his side's display and is confident they can mount a comeback in the return fixture at Parc des Princes next month.
"Madrid can hurt you with fast transitions. If we had been more accurate and if the referee had been a more balanced judge, we could have drawn or even won the game," he said.
"They're the favourites because they're the holders and they've won it three times out of the last four, but we have the capability to overcome them.
"The final score is obviously not positive, but we can come back from it. And my team played very well, I am very happy with them.
"The result makes you look at things in a different way. We have to be optimistic ahead of the second leg, and play again as we did today, when we created a lot of chances."