In a tournament heavy on goals and drama but relatively free of debatable decisions, Marco Devic's disallowed effort against England on Tuesday, which television replays suggested may have crossed the line, prompted outrage from the hosts.
The goal may not have saved Ukraine from elimination anyway but the referee in charge of the game, Hungary's Viktor Kassai, was one of four sent home on Wednesday as part of a standard pruning of officials before the quarter-finals.
Collina said it would have been "unfair" to expose Kassai to additional pressure following the row, which has prompted renewed calls for the introduction of goalline technology.
The bald-headed Italian, the game's best-known official before his retirement in 2005, insisted the decision did not undermine a system of extra officials which has been on trial in the Champions League and elsewhere for three years.
"This was human mistake made by a human being. Nevertheless this is the only problem we had with this experiment in roughly 1000 matches played," Collina said.
"[At Euro 2012] we had three goalline situations. Two of them were absolutely correct, the third was unfortunately wrong. Being wrong is one thing, saying that the ball was half a metre over is another and you know it. The ball was centimetres [over]."
He refused to be drawn on the case for introducing technology which proponents argue would remove the element of human error.
"The simple answer to that is that it is not for UEFA to decide. There is a meeting of the IFAB (International Football Association Board) on July 5," UEFA General Secretary Gianni Infantino told the same news conference.
"We do what we can. We think that in addition to seeing or not seeing the goal, the additional referee gives a lot of help. The fact that a mistake happened last night, the night before this press conference, is bad luck, but it should not hinder us in our very positive assessment of the last three years.
"We will see what the IFAB decides and we will see which leagues implement it if they do. But for the moment we have not seen any 100 percent success rate so far on any goal-line technology," Infantino added.
