Celtic manager Neil Lennon has branded the decision to award Udinese a late penalty in their Europa League match "disgraceful".
With four minutes left Gary Hooper was judged to have fouled defender Neuton inside the box, with Almen Abdi scoring the resulting spot kick.
But Lennon felt referee Bulent Yildirim rushed the decision and cost his side a valuable win.
"It is a shocking decision that has cost us three points," he said.
"There's not much we can do about it. He'll see the replay and make his own mind up about it.
"It was a disgraceful decision. Gary Hooper did everything he could stay out of the guy's way. He's just fallen into him.
"And the referee gave the decision straight away.
"Ours looked far more a penalty and he deliberated on it for about 30 seconds. I don't know what he was thinking of."
Celtic had got off to a perfect start when midfielder Ki Sung-yueng scored from the spot in the third minute after striker Gary Hooper had been fouled by Joel Ekstrand.
And despite conceding a late goal, Lennon was proud of his team's performance.
"I thought our play in general and the shape of team was very good," Lennon added.
"The discipline and concentration the players showed was very pleasing against a very good side. I'm delighted with the whole team.
"It was a very young team tonight and to play as well as that in an environment like that was very pleasing. I'm just disappointed we don't have the three points."
With Rennes drawing with Atletico Madrid Celtic are now bottom of Group I on goal difference.
"It was important to win the game tonight in terms of the group," Lennon added.
"We want to win our home games and but for that decision we would have.
"But there's still plenty of football to be played and we need to improve our away record especially now that we've dropped points at home."