The temperature around Glasgow is rising once again as Celtic and Rangers prepare to collide in another explosive Old Firm derby and Martin O’Neill has already thrown fuel onto the fire with a chilling message ahead of Sunday’s massive showdown at Celtic Park.
The legendary Irishman believes Parkhead is set to become an intimidating fortress for Rangers as the atmosphere reaches boiling point, with Celtic supporters fully behind the team once again after weeks of tension earlier in the season.
Speaking ahead of the clash, O’Neill admitted he expects a fierce response from Rangers despite their recent setbacks, but warned that the energy inside Celtic Park could become a decisive factor in the game.
“It’s an Old Firm game, so regardless of results before it, Rangers will still be strong,” O’Neill explained. “But the place will be rocking on Sunday.”
Those few words alone have already sent excitement racing through the Celtic support, with many fans believing the club is rediscovering the unity and intensity that made Parkhead one of the most feared stadiums in European football.
And according to O’Neill, that atmosphere is no longer just noise — it is directly impacting performances on the pitch.
Celtic’s Biggest Weapon Is Back
The return of the Green Brigade, combined with an improved relationship between supporters and the club hierarchy, has transformed the mood around Celtic in recent weeks.
Only a few months ago, the atmosphere around Parkhead felt fractured. Anti-board protests, supporter frustration, and inconsistent performances had created tension around the club. But now, after a run of strong results and renewed belief, the stadium is once again becoming a cauldron of noise.
O’Neill admitted that he initially underestimated how much the crowd situation was affecting players.
“There obviously was a bit of ill feeling at the time and there didn’t seem a united football club,” he said.
“But there’s no doubt about it now. The crowd being fully behind the team, even allowing for mistakes, has been very, very positive.”
That backing could prove massive on Sunday.
Old Firm matches are never decided purely by tactics or quality. Emotion, aggression, pressure, and atmosphere often shape these battles more than anything else. And with a packed Celtic Park roaring every tackle, every sprint, and every attack, Rangers could be walking into one of the most hostile environments they have faced all season.
Rangers Under Serious Pressure
The timing of this derby could hardly be worse for Rangers.
Back-to-back defeats have severely damaged their momentum heading into the most emotionally charged game in Scottish football. Confidence inside the squad appears fragile, while pressure from supporters continues to intensify.
Another defeat at Celtic Park would not only hand their rivals bragging rights — it could seriously damage their hopes of securing Champions League qualification and finishing the season strongly.
That is why O’Neill is refusing to underestimate the threat Rangers still pose.
He believes the Ibrox side will arrive desperate to respond after recent criticism and disappointment.
“But I think there’ll be a big reaction as well too,” O’Neill warned. “So we’ve got to be ready for that ourselves.”
Still, the former Celtic boss knows better than most what happens when Parkhead begins to shake during an Old Firm clash.
O’Neill’s Incredible Derby Record at Celtic Park
O’Neill’s words carry weight because of what he achieved during his first spell in charge of Celtic.
His very first Old Firm derby ended in a stunning 6-2 demolition of Rangers — a result still remembered as one of the greatest days in modern Celtic history.
From there, he turned Celtic Park into a nightmare venue for Rangers.
During his initial spell, O’Neill oversaw nine wins and two draws against Rangers at Parkhead, suffering only one defeat across years of derby battles at home.
Those statistics explain why supporters are hanging onto every word he says ahead of Sunday’s encounter.
He understands the emotional power of these fixtures perhaps better than anyone.
“When I go back to the cup game at Ibrox where we had our traditional allocation of fans, it’s so strong,” O’Neill reflected.
“It makes for a fantastic game and a fantastic atmosphere.”
Many supporters agree. The atmosphere inside Old Firm clashes has often suffered in recent years due to reduced away allocations and growing tensions between the clubs. But Sunday feels different.
There is a sense that Celtic Park is preparing for something special.
Celtic Fans Believe Again
Perhaps the biggest change surrounding Celtic right now is belief.
The squad looks more confident. The supporters are louder. The tension around the club has eased. And suddenly, there is genuine optimism building before the biggest fixture of the season.
Players such as Daizen Maeda and Reo Hatate appear to be thriving with the crowd fully behind them once more, while the energy from the stands has visibly lifted performances in recent weeks.
O’Neill clearly believes that emotional connection between supporters and players can push Celtic to another level.
“The players have fed on that as well,” he said.
That sentence may worry Rangers more than anything else.
Because if Celtic Park truly reaches the atmosphere O’Neill is predicting, Rangers will need nerves of steel just to survive the opening stages of this derby.
And if Celtic score first?
The noise could become unbearable.
Sunday’s Old Firm showdown already carried enormous stakes. But after Martin O’Neill’s explosive warning, the feeling around Glasgow is that Celtic Park is preparing to unleash chaos.