Joao Carvalho started and starred for Nottingham Forest against Middlesbrough.
The cries of ‘I told you so’ shook the foundations of the City Ground.
For many, a point had been proved.
A Portuguese playmaker had put in the performance, but twenty-odd thousand felt a part of it.
Calls which had been falling on deaf ears were finally heeded.
Those demanding more of a run from the Reds’ record signing were quick to bask in their own sense of personal glory.
Carvalho had just shown what he is all about.
Things are, however, not as black and white as some would have you believe.
This was not a case of merely giving a £13 million asset a few minutes.
If it really were as simple as that, then the 22-year-old would have been seen more frequently.
The issue, and O’Neill has never shied away from this, has been finding the right role for an enigmatic talent.
That has been easier said than done.
Against Aston Villa, in his only other start under the current boss, Carvalho looked a little out of sorts.
He was deployed as a No. 10.
Having been handed that squad number, and with his ability never in doubt, that is the job expected of him.
Forest, though, have not been playing to the strengths of a player in that post.
Under O’Neill the Reds have, on the whole, not seen enough of the ball to cater to the demands of a playmaker.
As a result, Carvalho could appear a little lost in the system.
Against Middlesbrough, a change in formation played into his hands.
No longer was he required to provide striking support.
Joe Lolley was now alongside him in those deep-lying spots, so the load could be shared.
Carvalho was free to drop a little deeper and influence proceedings where Forest need him most.
Much of his best work on Monday was carried out between the lines.
He was able to take the ball and get his head up with space in front and runners around him.
The Reds have lacked that creative spark for large parts of the 2018-19 campaign.
O’Neill deserves credit for having made another tweak which allowed Carvalho to light the fuse.
He has said in the Nottingham Post: “I think he is a player who you need to adapt the formation to – I think that is right – until he gets to know the real grit of this league.
“This was a beautiful day for playing football. It is not always like this, during the course of a 46-game season. But the whole experience this season will stand him in great stead for what is to come.”
This was, of course, one game.
And O’Neill is right to suggest that playing at home in the April sunshine is much easier than the fabled trip to Stoke on a wet and windy night in December.
Two men at the centre of a long-running debate have, however, shown what they can do.
A manager accused by many of being too stubborn to change his ways has found a solution.
And Carvalho has shown that he can be a match-winner when used correctly.
Both deserve credit for finding a happy compromise.
Maintaining those standards and keeping smiles on faces is now the challenge.
Will the same system and personnel be on display at QPR or will the experiments continue?