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Martin O'Neill rode into Glasgow in the summer of 2000 and immediately declared that Dick Advocaat's big-spending Rangers were Scottish football's benchmark.
By May 2001, the balance of power had seismically shifted in the city as Celtic were the team to beat.
On their way to a domestic treble, the club's first since 1969, O'Neill's men had laid down a mighty marker with a 6-2 caning of their rivals at Parkhead in August during his first experience of the Old Firm derby.
The domestic campaign culminated in the Hoops clinching the title at Parkhead against Tom Hendrie's St Mirren with Tommy Johnson cast in the role of unlikely hero when he scored the winning goal in a 1-0 win.
Scott Walker played for the Paisley outfit that fateful day in front of 60,440 expectant supporters. If football is full of sliding doors moments, then this was one for the ages 22 years ago.
O'Neill's men's trajectory was on the up and up while St Mirren under Hendrie were about to fall through the top-flight trapdoor that leads to the second tier.
Walker wasn't prepared to stand on ceremony or become an afterthought at a title party.
He does, however, readily admit that he was buoyed by the great atmosphere that day at Parkhead as the amphitheatre in Glasgow's east end shook to its rafters while St Mirren fought to save their Premier League skins.
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"That day at Celtic Park it felt like we were walking out in front of a 21st-century Colosseum," Walker told The Celtic Way. "We were surrounded by a baying audience. I remember walking out of the tunnel and being greeted with a wall of noise - an incredible sound which actually lifted me personally.
"Some players can react completely differently to that and get scared but it was the complete opposite for me, it spurred me on.
"St Mirren had to try to perform as well as survive in a way. We were fighting to stay in the league, so we had a reason to try to stop the title party.
"I think if any player goes into a match thinking 'we might get a draw' or 'we're going to lose' then they're not really a professional sportsman.
"We were trying to survive in the league so basically you were also trying to keep your job because if the club got relegated then you knew that some contracts would not be renewed.
"I remember the game well as Johnson actually mishit his effort and it squirmed under Ludovic Roy's body for the winner. Graham Fenton missed an absolute sitter to put us ahead in the game too.
"We had won the First Division title the year before and we went up and then came back down sadly. We performed well as individuals and collectively and acquitted ourselves excellently. We were pretty solid and the gameplan worked - to an extent. We kept Celtic at bay for long periods of the game."
To add insult to injury, when Walker did get his bearings he was greeted with the sight of Celtic stars like Henrik Larsson, Neil Lennon, Paul Lambert, Lubomir Moravcik and Alan Thompson to name but a few.
Walker knew he was witnessing something special at Celtic Park and, while he could match his opponents in fitness, he couldn't compete with their speed of thought as O'Neill's team moved Scottish football to its foundations.
"That Celtic team was full of brilliant football players with pure raw talent," Walker recalls. "I've always said you can be as fit as these guys but I think the way they all thought and processed information was amazing to watch.
"They were the best players because they mastered the information side of the game so quickly and that set them apart from everybody else in Scottish football that season.
"You got the feeling back then that Celtic were building something massive under O'Neill. He totally shook up Scottish football and, although he got a fair bit of money to spend, he challenged Rangers' dominance by spending his cash wisely.
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"On the title-winning day, I took stock of just how big and aggressive a team Celtic were becoming under O'Neill. That's how they played and it was very effective. The ball just kept coming back at you like a boomerang. Celtic were certainly a team on the way up and St Mirren were on their way down."
Walker earned a degree in sports therapy when he hung up his boots and now has his own private practice in Alloa called Scott Walker Sports Therapy and Pain Management. He has worked with St Mirren and St Johnstone and is currently with Queen of the South on a part-time basis.
He also jokingly revealed how he missed out on a prized possession as fellow Saints defender Barry McLaughlin beat him to the punch to snaffle Larsson's coveted title-winning jersey.
He said: "When the final whistle went that day I took my time going off the pitch and a moment to look around and sample the atmosphere. You always shake hands with opposition players but I didn't know if I was going to come up against top-class players like Lambert and Larsson ever again so I wished them all the best.
"It was an honour to play against them. I actually remember asking for Larsson's shirt but I didn't get it, I think Barry got it as he had asked him before me - he didn't hang about, it was the tightest anybody has ever marked Larsson in a game!"
Nobody could take it away from Martin O'Neill's men that season. As the 2000-01 title win showed, Celtic were now the benchmark.
This piece is an extract from the latest Celtic Digest newsletter, which is emailed out every weekday evening with a round-up of the day's top stories and exclusive analysis from The Celtic Way team.
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