Yet those attacking bursts were few and far between and it was our good fortune that Denmark lacked the quality and also the ambition to break down an Ireland team content to get men behind the ball.
Christian Eriksen, on a long scoring streak for his country, looked his country's biggest threat, but by the end of the night he was hoofing it along with the rest of his team, as they sank to their opponents' level.
"Age [Hareide] said last night in the press conference that he thinks they are capable of scoring at the Aviva - I wouldn't doubt that", said O'Neill.
"I think some of the players can draw on part of that but I think they'll probably try to create their own experiences".
"We'll be hard to beat, disciplined", Duffy said.
Ireland needed a play-off to secure their place at Euro 2016, beating Bosnia 2-0 at home following a 1-1 draw in the first leg a nd O'Neill is hoping history repeats itself. A 0-0 draw in Denmark has left the Boys in Green in need of a goal - a score draw will put the Danes through to the World Cup.
We are 90 minutes away from our first World Cup since 2002 and Martin and his coaching staff would have jumped at the opportunity in front of us now if it was offered to us at the start of this qualifying campaign. "I don't know if Ireland will do it". They've got players who can cut you open. When our time is to score, that will be, we've just got to take it easy and see what happens. "We have to take the pressure".
Asked whether he expected to be man-marked, Eriksen replied: "I have been man-marked several times before, but I'm not sure if Ireland will do it. We'll try and stay in the game as long as we can and we're confident we can score goals against them at home".