Roma forward Edin Dzeko questioned referee Danny Makkelie's courage after their 4-1 defeat at Barcelona in the Champions League on Wednesday evening.
The Bosnian went down inside the area in the 10th minute under the challenge of Nelson Semedo with replays of the incident confirming there was contact, but the Dutch official waved play on.
He later gave only a free kick when Lorenzo Pellegrini was fouled, with replays again showing the contact had taken place inside the penalty area. Dzeko was unhappy that neither were given and suggested Makkelie had been intimidated by the packed Camp Nou.
"It was a penalty on me and the referee has got to have the courage to give it against Barcelona," he told Mediaset.
"If we are in the quarterfinals too, then we deserve to be here just like them, so he's got to be even in his judgment.
"If he gives the penalties, it changes the game."
Goalkeeper Alisson was a little more philosophical, although he too felt that the referee got things wrong.
"Mistakes are part of football and we work hard so we don't make them, but in games they are going to happen," he said. "Whether they are our errors or those of the referee, we have to keep our heads up and continue to work even harder."
Roma left Barcelona with a result which leaves them with a mountain to climb in the second leg.
"We certainly played a great game in terms of our attitude," said coach Eusebio Di Francesco to Mediaset.
"We cannot shift the responsibility on to others, but we showed the determination and what can I say? We were suddenly 3-0 down and didn't even realise what had happened.
"I think the result is too harsh given our performance, considering who we were up against. We committed small mistakes inside our area and were a bit slow dealing with some situations, It's a pity, but we did ourselves justice.
"In the end, we conceded soft goals. What I'm sorry about is that we lacked the quality in the final touches for our chances, but when you create so many against Barcelona, you need to score more goals."
Roma host Barcelona in the second leg next Tuesday, needing to win either 3-0 or by at least four goals to go through. A 4-1 result would force extra-time and potentially penalties, but any other result would see them fall at the quarterfinal stage for the fourth time.