It was the biggest decision any Irish manager has made since Saipan. To drop your captain, your talisman, your chief goal threat for a game of this nature was a massive call by Martin O'Neill.
Ultimately, it was not one I would have taken. Managers live or die by their decisions. And this one backfired because in a match where we needed a goal, we didn't have our best finisher in the box.
Yet I am not going to hang O'Neill for this one. I can understand his thought processes. At 34, Robbie's legs are not as energetic as they once were. More to the point, they aren't as mobile as Shane Long's, who has performed admirably for Southampton this season and who scored twice last weekend.
Just in case you need reminding, Southampton are second in the Premier League. He had form and youth on his side. His pace is electrifying. Logic existed in O'Neill's choice and when he burst across the Celtic Park grass to dispossess Grant Hanley in the 12th minute, you could see why O'Neill had opted for him.
Being a fellow thirtysomething, my sympathy was with Robbie because there comes a time in every player's career when you realise you are dispensable, that you won't be selected for every, single game.
That moment arrived on my doorstep some time ago. Last night was Robbie's turn. He will be devastated by what happened. These things hurt. And yet he had to be professional. He had to sacrifice his ego and remember he is the captain and that players look up to him.
He had to play a big part in the dressing-room and in the warm-up, cajoling, encouraging and pretending to his team-mates that all was okay in his world, even if, deep down, that world had come crashing down.
After half an hour, it seemed as if the world would come crashing down on Ireland. At that stage, they were under the cosh. Yet they defended brilliantly, Seamus Coleman proving particularly effective. Yet while he impressed, few others did. The performance in the first half was as poor as we have been in a while. We needed someone to get their foot on the ball. No one did that, whereas the Scots had Steven Naismith and Andy Robertson on top form.
Personally speaking, I found the match fascinating to watch because - if we are honest - so many international games are boring these days. There are times when I am sitting on my sofa watching an international and the temptation is to flick it over to another channel.
But last night was different. It was like an old-fashioned cup tie, with tackles flying in, cards being flashed and neither side capable of stringing five passes together because the intensity of the defending was so fierce. It became an all-out battle.
And it made me think of the point Roy Keane made last month during his whistle-stop tour of Britain and Ireland to promote his book. "Ireland-Scotland," he said, "will be a battle. The game will be about anything but tactics. They will go out the window."
The comment was a tactic in itself. By publicly suggesting that this showdown will be a blood-and-thunder affair, Keane was attempting to get inside the Scottish players' minds. It didn't work. Scotland were the better side in that opening half. Their big players performed whereas ours, Coleman aside, did not. The hostility towards Aiden McGeady had an effect, the movement of Naismith between the lines of midfield and attack had an even greater impact.
He was superb. And so, for the last 15 minutes of the first half, were Scotland. But Ireland survived to the break. And up until the goal, their performance improved after it. For me it seemed clear that the Irish players were caught up in the occasion in that first half but in the third quarter, we finally settled down.
I'd imagine O'Neill's calming words had an impact. His message would have been to play the game, not the occasion. And the difference was obvious. Suddenly we started to pass the ball around. Midfield was no longer bypassed. Darron Gibson increased his involvement.
Then Scotland scored. All of a sudden, tactics disappeared because nothing shapes a game as much as a goal. Formations are all well and good but when it boils down to the nitty gritty, a goal can deflate one team and provide an injection of confidence to another. So it proved last night.
From Scotland's perspective, this was a moment of brilliance from Shaun Maloney - a similar goal to the one he got for Wigan against Manchester United a few years ago, which saved the club from relegation.
Ireland will be annoyed, though. After doing the right thing initially, sending two men out for the short corner, uncertainty followed. Whose job was it to pick up Scott Brown? No one did the job. Brown made the pass, Maloney supplied the finish.
Sometimes you have to take your hat off and say it was a good finish but you also have to say that sometimes, players need to get organised quickly and not just stick to the pre-match plans that are given to them in the dressing-room. When you defend, you have to improvise. Ireland didn't. And it cost them.
So too did James McCarthy's absence. Midfield was where we lost it last night. We were outgunned by the Scots. And had McCarthy played then you have to wonder if a point could have been gained. Still, despite this defeat, the group remains wide open. It means we have to get something out of every game, I would suggest because this was a six-point swing.
The great, green vault of Celtic Park was, as promised, transformed into the taut bearpit that drew Irish blood. It was the night Gordon Strachan had prophesised, a gathering of Scottish clans keyed to almost unhinged emotion as they claimed critical Group D momentum.