A realistic Martin O'Neill has conceded that after their 3-0 defeat here his Celtic side will have to win their last two Champions' League games to be certain of progressing to the next stage of the competition.
However, the Bhoys manager is hopeful that, in the manner of Leeds United last season, his inexperienced team will learn quickly from their European reverses.
Speaking after Celtic's disappointing showing in the Estadio das Antas, O'Neill said: "I don't want to draw comparisons with Leeds, but they showed they were a good side last season and went far.
"This is just our fourth game of the Champions' League and don't forget Leeds took some severe beatings early on and we will try to qualify and learn from it as much as we can.
"Like all things, every game in the Champions' League is invigorating and I hope the lads learn from it."
David O'Leary's team recovered from away defeats by Barcelona and Real Madrid to progress to the semi-finals in their debut in the Champions' League. Yet Celtic's hopes of emulating them are hampered by their results against Porto, having only beaten the Portuguese side 1-0 in Glasgow
"Our record against Porto is now bad so I think we need 12 points," O'Neill admitted. "We have to go to Rosenborg and get something from the game.
"Juventus have eight points, Porto have seven and we have six. If Juventus win they will go to 11 and then you have to assume that Porto, on that form, will beat Rosenborg at home. That will take them to 10 points so we will probably have to win our next two games."
O'Neill maintained that Porto would have beaten most European sides with the sort of performance they produced on Wednesday night. However, he thought his side's poor display made them look better than they actually were.
"I thought they played very well and showed that they are a very, very good team, make no mistake about it," he said.
"They are a good side, but our own disappointing performance was part of it all. But no matter how well Porto played last night, we allowed them to play really well without responding in any shape or form.
"I think everyone was second to the ball and we made some really silly errors over the course of the game and not all of them went punished."Reuse content