The thrashing left the Catalan side facing a round-of-16 elimination for the first time since 2007.
Sacchi -- who spent time in Spain as Real Madrid's director of football and also coached Atletico -- praised Barca's success over the last decade but suggested losing their principles had led to the humiliating defeat.
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"For some time, Barcelona have not been the old Barcelona," he told Sport.
"Even in La Liga they beat the weak clubs with ease but struggle with stronger sides. You no longer see that aggressive, organised and hungry team we so admired.