Football is a simple game. When you have the better players and do the basics right, you will come out on top more often than not. That idea often gets lost these days. This evening was a great reminder of it. Wilfried Nancy came in as Celtic manager and won just twice in eight attempts, trying in vain to implement his 3-4-3 system, that had looked doomed from the start.
A lot of people were quick to criticise the players during the Nancy era. But having seen the same group win seven out of eight games under Martin O'Neill, I, for one, did not join in on the criticism.
Now, O'Neill is back in charge of the team, and this looks like a proper Celtic team again. Of course, there are areas in need of improvement. The performance against Dundee United was proof though that they should not have been losing the games that they were under Nancy, and it was not down to the players.
O'Neill has got this team playing like Celtic Football Club again. And the fans could not have been happier about it.
'Celtic Football Club are back' - Fans react to Martin O'Neill masterclass
As one fan wrote after Daizen Maeda made it 4-0 to O'Neill's side: "Spread the news: Celtic Football Club are back!"
Another added: "Dear Martin O‘Neill, thank you for taking care of Celtic."
A third said: "Unreal today, can you imagine what Martin would do with few signings?"
And that is something that the board need to remember. Just because the team are looking good under O'Neill does not mean that they can overlook the need for signings in this winter window.
O'Neill himself has called for additions while talking to the media recently. Hopefully, he will be given the backing that he deserves, especially after this display from the team.
There is still a long way to go. It is still just one win and three points. But it was also a reminder of what Celtic are capable of, in case some around Scotland had forgotten.