Jack Grealish and Phil Foden were dropped for clash against Newcastle United.
The duo have been pictured in a nightclub prior to their game against the Magpies and Guardiola decided to drop them for the night.
The club was unhappy with the condition the duo arrived at training the next day.
Pep has warned his players over off-field behaviour during Christmas and New Year’s eve.
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Guardiola said on Sunday: “It was not rotation. I decided on this team because they deserved to play today, these guys and not the other ones.
“At Christmas time I pay a lot of attention to behaviour on and off the pitch. And when off the pitch is not proper, they are not going to play.
“So we have to be focused all the time because of distractions at Christmas time and everything that happens – you have to still be focused.”