The Celtic players were put through their paces at Lennoxtown ahead of a potential title-decider.
Ange Postecoglou's men boast a three-point lead at the top of the Premiership, but things could change quickly in a full-throttle title race.
A win for Rangers will see Gio van Bronckhorst's men move level on points with just goal difference separating the sides.
It's a potential turning point for both teams and Postecoglou has plenty to think about going into Sunday's showdown.
With an almost fully fit squad, the Australian has plenty to ponder ahead of the clash at Ibrox.
Here are five things we spotted at Lennoxtown before the top of the table clash.
Ready to Kyo-go
It's been the question on everyone's lips - will Kyogo Furuhashi be ready to face Rangers?
Today Postecoglou gave the answer every Celtic fan wanted to hear going into Sunday's showdown.
The striker was put through his paces at Lennoxtown today and is available for selection for the first time since December.
He was pictured in a foot-race with international teammate Daizen Maeda - and looked to be winning as the livewire attacker tries to prove he is is ready for a key role at Ibrox.
But will Celtic roll the dice and add the Kyogo fear factor to the bench? Or could he even have a chance to make his mark on the game from the start?
All smiles from Rogic
Going into the game on Sunday, Tom Rogic was another potential injury headache for Ange Postecoglou.
The midfielder limped off after a crunching tackle from Ross County defender Kayne Ramsay in the last Premiership outing and missed Australia's international double header.
However, he looked to be back to full fitness going into the showdown with Rangers.
He was all smiles as as he led his teammates in their training drills at Lennoxtown, and having made a huge impact at Ibrox before he will be desperate for a start.
Positive attitude from the stoppers
While they won't have to face Alfredo Morelos, Rangers have plenty of firepower that could make the difference on derby day.
Ryan Kent, Kemar Roofe, Aaron Ramsey, Joe Aribo, James Tavernier, Fashion Sakala...it's a worrying list of names for Joe Hart and Scott Bain ahead of crossing the Glasgow divide.
If they are nervous you wouldn't know as the pair played up to the cameras at Lennoxtown.
Bain gave a big thumbs up and will be hoping he is still smiling after the key derby clash.
Pressure? What pressure?
It feels like the biggest derby day clash in years with the Premiership title hanging in the balance.
A win for Celtic and it's a massive advantage in the title race, defeat and Rangers are well back in the hunt.
You'd think Postecoglou and his management team would be feeling the pressure, but if they are you couldn't tell at Lennoxtown.
John Kennedy and the boss shared a laugh in the sunshine just days away from a potentially season-defining fixture. Maybe Gavin Strachan has an April Fools joke up his sleeve....
Having a knees up
But will it be the same for Giorgios Giakoumakis on Sunday?
The striker sparked controversy with comments insisting Celtic are better than Rangers in every department.
That's sparked the ire of Ibrox fans and midfielder Ryan Jack - who branded the towering Greece cap "disrespectful."
He was all business at Lennoxtown as he went through his paces after netting five goals in his last four games. His knees were up at training, will it be a similar scene if he nets in Govan on Sunday?
