The Republic of Ireland returned from Denmark with their World Cup hopes finely poised after the first leg of their play-off ended in stalemate.
Here, Press Association Sport's Damian Spellman takes a look at what we learned from a tight 90 minutes in Copenhagen.
Martin O'Neill apparently cut short his training session at the Parken Stadium on the eve of the game amid fears that Danish eyes were watching rather too closely.
What the Danes might have learned that they did not already know is debatable, however, as the visitors set up as they so often do to defend deep and in numbers and trust themselves to repel whatever was thrown at them, which they did in pugnacious fashion.
The reason that Shay Given's retirement from international football has not been felt as deeply as that of Robbie Keane is because Ireland are better at preventing goals than we are at scoring them.
Having edged ahead of Keiren Westwood, David Forde and Rob Elliot in recent years, Randolph has become an increasingly central figure and he produced three vital saves in Copenhagen to keep Denmark at bay.
There were flashes of Tottenham schemer Eriksen's rich talent in the first leg, but fewer than coach Age Hareide might have hoped.
However, Eriksen's club form suggests that if he is allowed him time and space - something that was done relatively infrequently on Saturday evening - in Dublin, he could punish us.
It was after Eriksen has found himself with clear grass ahead of him at the Parken Stadium that he troubled Randolph with a swerving long-range effort, which the keeper managed to fend off, but only to wide-man Sisto.
However, the Celta Vigo player rolled the ball inches past the post, a miss which may live with him for some time if Denmark fail to progress.
Nineteen men - 10 of them Irish and nine Danes - went into the first leg on a booking and knowing a second would rule them out of the game at the Aviva Stadium.
But despite presiding over a competitive encounter, Serbian referee Milorad Mazic kept his cards in his pocket to allow all 19 to live to fight another day.