The Premier League’s bottom club defied the odds and ran out comfortable 2-0 winners thanks to first half goals from Sekou Mara and Moussa Djenepo.
Even the introductions of Kevin De Bruyne and Erling Haaland after the restart failed to spark City into action as they succumbed to defeat in a competition they have dominated in recent seasons.
Guardiola’s side are back in action on Saturday when they face a daunting trip to Old Trafford for the Manchester derby against Erik ten Hag’s rapidly improving outfit.
City crushed United 6-3 in the reverse fixture earlier this season when both Haaland and Phil Foden scored hat-tricks, but Guardiola accepts United are in a completely different place right now under their new manager and will pose a real threat.
Guardiola said: ‘Every game is different, different competition but of course if you perform in this way we will not have a chance, in the moment they have and for many years they were looking for to stay in this position.
‘We know exactly what we have to do to play better and that’s what we are going to try to do.’
Guardiola also defended his decision to rest Haaland and De Bruyne from the start, pointing out that neither player featured in Sunday’s 4-0 FA Cup drubbing of Chelsea.
He added: ‘I leave them on the bench against Chelsea and you didn’t ask me that question because we won.
‘Always I believe when you play four competitions I have the feeling that you have to use everyone you have to be ready.
‘And the guys that don’t play have to do something with your body language to help the guys and everybody be involved. So who knows if Erling and Kevin it could have been different. I don’t know.
‘We tried to do our best. We rotated our team after we played Chelsea in the Premier League and we won and people say how nice is the decision.
‘I understand this business we want everyone to be invovled but today was not the case. I had the feeling today it doesn’t matter the line-up what I do we will perform in this way.’