Clyde goal hero Eddie Malone claims Roy Keane and Co underestimated the First Division giantkillers in the Tennent's Scottish Cup.
The former Manchester United captain's debut was a disaster as the holders and SPL leaders crashed out of the competition to one of the worst results in their history.
Malone scored what turned out to be the winner - for a side who were only assembled by Graham Roberts after pre-season trials - between Craig Bryson's shock opener and Maciej Zurawski's late consolation.
And the youngster believes Keane and his new team-mates simply did not take Clyde seriously enough - which proved so costly.
Malone said: 'We knew Roy Keane and Neil Lennon were going to pass the ball about and make things tick for Celtic.
'But we knew if we got in and about their ankles and did not let them get their heads up then we would have a chance.
'I don't think they came here expecting an easy afternoon but they underestimated us a wee bit. They never expected what they got.'
Keane was a class act after the match as he paused to sign autographs for children on the way to the team coach.
But the Republic of Ireland international and his new colleagues were surprisingly out-fought and even outclassed by the Broadwood club.
Malone added: 'I knew we could match them but I never thought we could pummel them like we did in the first-half.
'I was surprised at how much we got at them and I never thought they would come back at us because they had just one chance.'
Roberts fears big clubs will come sniffing around his players but Malone believes his team-mates will soon be competing with Celtic in the top-flight on a regular basis without leaving.
'This club took me and gave me a big chance,' he continued. 'I was at St Johnstone and Graham took me and gave me a two-year deal.
'It's the same with a lot of the boys and most of the boys are signing up for next year.
'If we can keep this team for next year we have definitely got a great chance of getting into the SPL. We showed we could hold our own there.
'We've got boys playing for peanuts and we wanted to put ourselves on the map again.
'Some clubs thought we weren't good enough and released a lot of the boys and we have showed them something.'
Celtic manager Gordon Strachan admitted his side were worse than they were against Artmedia Bratislava in his first game in charge - the 5-0 Champions League qualifying drubbing in Slovakia.
He sighed: 'The performance was worse than the Artmedia one. I could never see Artmedia scoring a goal but I could see Clyde scoring.
'It's been all right for a wee while but it has gone downhill the last few hours.'