Possible yes in a 0.01% kind of way.
Also over confidence to me is the first step to failure - not lack of it.
Confidence is a thing many players search years for, its like a drug where you must have to it perform to your optimum best. But then there is also over confidence and I have seen it in many teams over the years - including Barca.
Being over confident means you are taking things for granted, you lose focus, you take short cuts in your work and you think you have done all the hard work and you can now sit back and relax because other teams will just fall at your feet.
In reality you have to keep working, remain humble and remain focussed.
The biggest case of over confidence I have seen in a football match involves Barcelona.
It was the 1994 European Cup Final.