Celtic are through to the semi-final of the Scottish Cup after a routine 3-0 away victory against Dundee United at Tannadice.
There was an element of novelty heading into the game this week due to the kick-off time of 7.45pm on a Monday evening.
With a few ales enjoyed beforehand, the Celtic fans were in full voice pre-match and that continued throughout the 90 minutes, even if they had to endure a bit of a tough watch at times.
It wasn't a classic cup tie by any stretch of the imagination, though a lot of that can be blamed on the surface in Dundee. The bobbling, dry pitch made it difficult for Celtic's ball players to pop possession around in their usual, vibrant style.
Still, the Hoops controlled things, as even though United put up a decent fight, getting in the faces of the Celtic backline, Joe Hart was never called into action to any kind of troubling degree.
Indeed, pre-match nerves that any Celtic fan may have been feeling were quickly evaporated as the visitors opened the scoring just 12 minutes in.
From a corner-kick routine down the right, the ball found its way to Callum McGregor, who fired a deflected strike beyond goalkeeper Benjamin Siegrist.
Postecoglou's heart would have been in his mouth when Reo Hatate went in late on Kieran Freeman, but the punishment of a yellow card was probably the correct decision.
With 10 minutes to go in the first half, Celtic had the ball in the back of the Dundee Utd net again, with Daizen Maeda squeezing a finish home at the back post.
But, the goal was disallowed due to a handball from Giorgos Giakoumakis in the build-up.
The home side came out after half-time with a spring in their step similar to the start of the game, but Celtic hauled the momentum back in their favour with a second goal in the 57th minute. Usually an impressive performer against Celtic, Siegrist dropped the ball right at the feet of Giakoumakis a yard out, with the big Greek accepting the gift with an easy finish.
As the game progressed the pitch got worse, with players falling, the ball bobbling, and passes not coming off.
Indeed, Celtic had numerous bursts through on the counter that fell apart due to the final ball going wayward.
With 15 minutes remaining, Postecoglou made a treble substitution, with Karamoko Dembele, James McCarthy and Mikey Johnston entering the action.
Dembele was impressive in his cameo, and played a part in the third goal with a direct run into the box. It was his attempted strike that deflected into the path of Giakoumakis for another predatory finish.
The draw for the semi-final of the Scottish Cup took place after events at Tannadice, and Celtic received a derby against Rangers, with Hearts and Hibs featuring in the other semi-final set to take place at Hampden.
Following the game, Postecoglou praised the efforts of his players in what was tough surroundings.
"It was a tricky one for us, coming here. They're a tough team to beat, the pitch isn't great," he said on Premier Sports.
"With all that in context, we worked really hard, we looked really bright.
"We tried to play as aggressively as we possibly could, under the conditions. Credit to the boys, I thought it was a good effort.
"It was a great atmosphere, the supporters got right behind us. We had to be up for it, but we handled it well."
Celtic Exchange Man of the Match: Callum McGregor
Giakoumakis may have got two goals, but it was McGregor who was the most important player again for the Celts.
While many other players struggled on the surface, the club captain kept his composure and acclimatised himself to it, eventually running things from midfield.
He got on the scoresheet and was unlucky not to get another goal, too, as he sent an effort just wide of the post.
Celtic's next match
Celtic will be hoping to take the momentum gained from their Cup win into the Scottish Premiership as they face Ross County on Saturday afternoon at 3pm.
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