And so we are here again.

This time 12 months ago the rain pelted down at Hampden with a drookit Ronny Deila scurrying inside to take his seat. On the eve of a William Hill Scottish Cup semi-final with Rangers, the Celtic manager spoke about how the match up between the pair was a 'special game'.

Not even the Norwegian could have imagined just how the events of that Sunday, or the fall out, that would come from it.

As Rangers edged out Deila's team on penalties, it was the beginning of the end of his tenure at Parkhead, and, in many respects, Mark Warburton's at Ibrox.

The reported over-exuberance in the Rangers half of the directors' box at the national stadium is believed to have sparked the Celtic board into action as Brendan Rodgers was sought out.

While the Rangers players celebrated on the newly-laid Hampden pitch, the seed had already been planted in the mind of Dermot Desmond that a change was needed if Celtic were to grow.

It's hard to think it was a game that contributed to the demise of both men who stood in the technical area that Sunday afternoon.

Deila's declaration he was going to leave in the summer followed in the immediate aftermath, while the result was used not only as a yard stick to measure how far Rangers had gone backwards in the early parts of this season, but one to beat their manager with before he resigned/was sacked/disrespectfully went into hibernation until Nottingham Forest phoned him.

Despite having just won the Championship little under a fortnight earlier, the gulf between the two teams was seen as far too vast for the team in light blue to bridge.

As it transpired, Rangers were by far the better team on the day, leading in normal time and extra-time again before Tom Rogic ballooned a spot kick over the bar. It was no more than both sides deserved.

One year on, the stage and billing is the same even if both managers have changed. Rodgers and Caixinha will occupy the technical areas this time, but already most are heavily tipping Celtic to win at the very round they faltered last time out.

They have won all but one of the four Old Firm games so far this season while drawing the last, after all.

Yet, despite their domestic dominance and how they have come to this point of the season unbeaten with two trophies already tucked away, this surely is the most anticipated and potentially closest match up between the pair yet.

Rangers have been a mile off competing with Celtic over the course of this season but, away from that 5-1 demolition at Parkhead back in September, have run their rivals close in terms of scorelines.

In the League Cup semi-final back in October it took extra-time to deliver one goal to separate them, on Hogmanay Celtic rightly just edged it 2-1 while last time out a battling Rangers claimed a 1-1 draw in Glasgow's East End.

The arrival of Caixinha has added another dynamic to this enthralling prospect. Under the stewardship of the Portuguese Rangers are unbeaten and have recorded an emphatic 3-0 win at Pittodrie along the way.

Of course, nothing can prepare him for the heat of an Old Firm game. But, with that form, the belief that goes with it and the slightly diluted intensity from playing at Hampden, I don't believe we will see anything near the mauling we witnessed last September or even the one-sided affair when both teams met at the national stadium, despite the tight scoreline.

Celtic have taken their foot off the gas since clinching the league at Tynecastle. Three games have brought just one win and no clean sheets.

Rangers proved in the 1-1 game at Parkhead that if their workrate and intensity outdoes that of Celtic, they can cause problems. Given the drop off in form of the Parkhead backline and the slowing of results, this will be a concern to Rodgers.

For the first time in 12 months, Scottish football finally has an Old Firm game that Rangers have the potential of winning.

Like previous meetings, though, the outcome of this game will come down to what Celtic do. If they turn up, Rangers won't have a hope. If not, the celebrations of a year ago in the blue half of Hampden could well be replicated.