Although top spot in Group in D was not out of reach for either side before kick-off, Serbia's 1-0 victory over Georgia gained them automatic qualification to Russian Federation 2018 and forced Martin O'Neill's side into the play-offs. "That last half hour seemed an eternity". We had to withstand pressure but we knew at some stage we would have to try to win the game and we did it.
Italy are a side stacked with talent but we got on alright the last time we met.
Allen had set Wales' early tempo and his departure was a boost for the Republic, who had shown belated signs of settling and tested Wayne Hennessey for the first time through Robbie Brady. We now had something to hold onto.
O'Neill spoke alongside McClean in his post-match interview with RTÉ: "He [McClean] has just been magnificent".
"He's brilliant. He might not have the same total ability as Gareth Bale, but he's been great for us. He's been a talisman".
It was the third time McClean has hit the victor in Ireland's qualifying campaign and he was delighted with their response to adversity.
But the Republic defence would not budge and Wales, who had started the evening clinging to hopes that they could win automatic qualification if Serbia had lost, were left with nothing.
"I said a while ago there: Bring them on".
And we'll beat them as well.
In the absence of key man Gareth Bale, it was Ireland's James McClean who took centre stage as he fired in a brilliant strike to keep Irish hopes of a place at Russian Federation 2018 alive.
"Certainly, the view among the players, is that if Russian Federation is available to us, then he would very much be in the forefront of our thoughts".
"It was really great tonight". "Every single game I play is for her", he said.
Attention now turns to the playoff draw which will take place next week.
'Do I fear teams in there?
Regarding the seeding, the Republic of Ireland won't be one of the four seeded teams due to their Federation Internationale de Football Association ranking while Northern Ireland's failure to beat Norway in their final qualifier will also mean that they'll be unseeded.
O'Neill confirmed that Jon Walters will miss out on the playoff but he wasn't quite ruling out the return of his captain Seamus Coleman.
Having come so close to qualifying, Welsh football his hurting from Monday's defeat, and questions are now being asked about manager Chris Coleman's future.
The day after defeat to Portugal in Lyon 15 months ago, Coleman was clear that he would move on after the 2018 qualifying campaign.
And it clearly affected the home side, with Coleman forced into a tactical re-shuffle with Jonny Williams coming on and Aaron Ramsey forced to drop deeper in midfield.
It's exactly what we want to hear from the players. "They are inconsolable but they should be very proud". It's been a privilege to work with these players.
He said: "I thanked them for their work, their passion, for making the nation proud".