Celtic restored their nine-point lead over Rangers at the top of the Scottish Premiership with a 5-1 win over St Mirren, but the champions were made to work for their victory by coming from behind.
Ange Postecoglou's side were given a harsh welcome back to life in the league after their League Cup triumph last weekend, as Mark O'Hara's penalty put the Buddies ahead after six minutes following Greg Taylor's handball.
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St Mirren were impressively holding out the champions for the rest of the first half but the game hinged on Charles Dunne's red card after 38 minutes for bringing down Kyogo Furuhashi as last man.
The hosts held on for half-time but two goals in five minutes from Jota and Alistair Johnston turned the game on its head after the interval. More quickfire strikes from substitutes Liel Abada, Matt O'Riley and a penalty from Hyeongyu Oh added further punishment to St Mirren.
The five goals scored by Celtic means they have reached 250 goals under Postecoglou, in the manager's 99th game in charge of the club.
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How clinical Celtic stayed patient to win
Celtic came into this match on the back of their Viaplay Cup celebrations - but also with a record of failing to win their last four matches that have followed the League Cup final.
And the champions were met with more problems early on as VAR deemed that Taylor had handled after just three minutes following Alex Greive's flick forward.
St Mirren captain O'Hara stepped up to cooly put the ball past Joe Hart to score his third goal of the season against Celtic.
Stephen Robinson's Buddies came into the game unbeaten in the league this season after scoring the first goal - and the hosts kept the league leaders at bay for most of the half by restricting them to long-range shots.
Reo Hatate saw two long-range efforts fly over, before goalkeeper Trevor Carson was forced to divert Jota's strike in the area over the bar with his chest.
St Mirren were holding on until half-time but then suffered a massive blow from their own making just seven minutes before the interval.
Dunne expected goalkeeper Carson to come out to collect a through forward but the mix-up in communication allowed Kyogo to nip ahead of him and through on goal.
Dunne brought the Celtic striker down on the edge of the box and was given his marching orders - with VAR overturning the referee's original call of a penalty to a free-kick.
St Mirren's resistance lasted until 11 minutes after half-time as the introduction of Abada proved to be impactful.
The Celtic winger fed Aaron Mooy down the right flank, with the Australian's cross blocked as far as Jota, who poked home from close range.
Mooy was the orchestrator of Celtic's second goal just five minutes later as his free-kick was headed in by Johnston at the far post for the Canadian's first goal for the champions.
Nine minutes later, the low-on-confidence St Mirren players succumbed to a third goal. It was Mooy with another assist as his pass found Abada in the box. The Israeli winger then burst past two players before slamming past Carson.
Abada then turned provider just two minutes later as his cross was met by O'Riley's first-time volley, the ball nestling into the net for the midfielder's first league goal of the season.
And there was a first Celtic league goal for Oh as well, with the South Korean striker being felled by Alex Gogic in the area. VAR would not frustrate Celtic this time and the 22-year-old saw his spot kick squirm under Carson for the fifth.
Oh nearly grabbed a sixth as O'Riley's cross bounced off his head and wide of the St Mirren gola - but five would be enough for Celtic.
Walker vs Boyd on penalty call
VAR played a major role in the first half, with Sky Sports pundits Andy Walker and Kris Boyd disagreeing over whether St Mirren were rightly given a spot kick.
Here is what the two pundits had to say:
Andy Walker: "Just put it down to the long list of ridiculous decisions we are seeing from VAR. There is no way VAR should be getting involved there. I have no idea where Greg Taylor can go or put his hand. The referee is in a perfect position and sees nothing. But Andrew Dallas [VAR] wants to give a penalty and I have no idea why.
"My only surprise is that all the clubs are putting up with this ridiculous interpretation of the laws of the game. Everyone seems really pleased with it when players are getting punished left, right and centre every week."
Kris Boyd: "It is a penalty. It's clear that his hand is out. For me, it's a penalty kick. There's the argument of taking your arm out of the way, but Greives is getting round the other side."
Postecoglou: Subs changed the game
Celtic manager Ange Postecoglou speaking to Sky Sports:
"It was a good little challenge for us. We know it's a difficult place to come to and we had to be really disciplined even after we went a man down. We had to play our football and it was a fantastic input from those who came on, they really put the pressure on.
"The strength of the squad is only measured by the impact the players make. You can have a really strong squad, but if they're not in the right kind of mindset where they're not starting or not starring, then having a good squad doesn't matter. The boys are good where when they're playing, they are ready to play and it was a massive contribution.
On whether the red card changed the game. "It doesn't change their approach, they will still sit deep and put bodies in the box. We stayed calm and looked for the best options. Liel made a good impact. We got five but could have got a couple more.
On the penalty call. "You have to ask Greg if it's harsh on him. But if it's harsh on us, I don't know. VAR doesn't miss anything, it didn't miss anything today.
"When you go a goal down, you have to maintain your composure and we did that. Kyogo gets all the headlines with his goals but his ability to press opposition gets unnoticed and he got a player sent off because he didn't give them a moment's peace."
Robinson: Celtic tired us down
St Mirren manager Stephen Robinson speaking to Sky Sports:
"It's clear to see that it's a difficult proposition with 11 men let alone 10. We gave ourselves a good platform, everything we wanted. We were 1-0 up, Celtic coming onto us and we went two versus two on our breakaways. The decision is a poor decision, it's a red card. It makes a game very, very difficult.
"Three or four of the goals, our decision-making could be better. You have to give credit to them, they wear you down and you tire and make poor decisions.
"They get the first goal and we're trying to change it to give us another platform up top with Tony Watt and they score from a free-kick. We won't let this define our season, the second half they blew us away with their movement. We have to reset ourselves. For 45 minutes, it was the perfect game plan."
What's next?
Celtic's next Scottish Premiership match is at home to Hearts on Wednesday night. Kick-off 7.45pm.
St Mirren travel to Dundee United for their next league game on 18 March. Kick-off 3pm.