Colombia striker Jhon Duran scored with a penalty after just five minutes in Lisbon after being fouled by Hoops defender Dane Murray and added a second in the 35th minute, after defender Alexander Bah had notched midway through the first half.

Celtic reduced the deficit through Camilo Duran in the 63rd minute before Benfica substitute Vangelis Pavlidis fired in a fourth with two minutes remaining.

Celtic lost 3-1 at home to Hungarian outfit Ferencvaros in their first Europa League game at Parkhead, but boss O’Neill insists he witnessed enough in the second half performance in Portugal to give him belief.

He told TNT Sports: “We started quite well, we forced a corner early on, and just trying to get into the game, they got a goal. The last thing you want to do is concede so early on.

“And then at 2-0 we’ve got a great, great chance to make it 2-1 and within a few minutes they make it 3-0.

“We could have capitulated, but I thought the second-half performance was really terrific.

“It was a game of two halves. We created chance after chance, we should have scored more goals.

“And of course, you’re going to leave yourself a bit open at the end.

“But I tell you, the second-half performance gives me what I would call the determination and I think we can still qualify.

“I know it’s down to six games, but we want to qualify for this competition to get into the knockout stages. We can still do it.”

O’Neill admitted Benfica’s second goal could have been avoided when Bah was left alone to side-foot in a cross from impressive 20-year-old Argentinian Gianluca Prestianni, but was keen to keep stressing the positives.

The Northern Irishman said: “One of their goals is just a little dink across, and we’re coming out instead of defending it properly, and that’s really poor from our viewpoint.

“You can’t afford to do that. I don’t think you can afford to do that in any game, never mind a game of this magnitude.

“But trying to pick up from that, the second half, as I said to you, we could have capitulated, it could have been all over.

“But we came roaring back, the substitutes did brilliantly and we could have scored a number of goals.

“Yes, I accept the fact that then, on the break, they could have scored themselves – as they did for the fourth goal.

“But overall, I’m really, really delighted with the second-half performance, and it’s a shame that we conceded the three goals first of all.”