Confident Alan Stubbs has written off Rangers' title hopes and insists Ange Postecoglou must push for a Treble.
A 2-1 victory at Ibrox secured Celtic' s first win at Ibrox since 2019 and crucially moved them six points clear at the top of the Premiership.
They have one hand on the title heading into the final six games and have already lifted the Premier Sports Cup this season.
Rangers stand in Celtic's way of reaching the Scottish Cup final when they face off at Hampden in two weeks' time.
Stubbs reckons that the league is over for Rangers follow Sunday's showdown and believes a Treble is on it's way to Parkhead.
The former Celtic hero said: "I think the title race is over.
"I think Sunday was a defining moment. Rangers have still got to go to Celtic Park, where I think the gap is only going to get bigger.
"Celtic can afford to lose two games and they will still win by goal difference.
"I think it is a foregone conclusion now. I would think the treble will be in their sights now.
"They've got one piece of silverware in the locker already, the league looks done and dusted, and they meet each other in the Scottish Cup semi-final, so I don't think anyone would rule out the treble."
Stubbs admits he didn't see the dramatic turnaround from last season when Postecoglou stepped into the Celtic Park hot seat.
With a massive overhaul taking place behind the scenes in at board level and on the pitch, Stubbs insists the manager deserves all of the credit for the turnaround from last season's disaster.
He added: "Could I envisage Celtic being in this position? Honestly, no.
"I thought Celtic would certainly improve and I thought they would be closer to Rangers, but the transformation and the turnaround has been remarkable.
"Being honest, I don't think any Celtic supporter would have thought they could turn everything round as quickly as they have.
"It was a huge rebuild. It wasn't just on the pitch either, Ange inherited a situation off the pitch as well, because Peter Lawwell was moving on and a new chief executive came in who left pretty quickly. It was a changing of the guard and there were also recruitment issues.
"There was an awful lot going on off the pitch and on the pitch Celtic were in a mess from the previous season.
"Ange has come in and done nothing short of a fantastic job. His personality has certainly helped the situation. He comes across as a calm individual who knows exactly what he wants.
"Virtually every signing he's made has been a success and it's very rare that that happens.
"He has to take a lot of credit for that because, apart from the obvious ones who people knew, I think a lot of people were thinking, 'Who? I've never heard of them' with a lot of the signings, particularly the ones from Asia.
"But they've been brilliant and they've taken the Premiership by storm this season."
