The England pair had impressed in the 7-0 demolition of Leeds United at the Etihad Stadium five days earlier, but both were left on the substitutes’ bench for the 4-0 win at St James’ Park and Guardiola made it clear that his team selection had nothing to do with rotation.
Grealish and Foden are understood to have gone out together after the Leeds game and City were unhappy with the condition in which they reported the next day for a recovery session.
Guardiola was in Barcelona on Wednesday to attend Sergio Aguero’s retirement announcement and it is understood that the manager was left distinctly unimpressed when the news was relayed to him.
And the City manager left Grealish and Foden in no doubt that he would not tolerate a repeat with his remarks after the Newcastle match.
Asked why he made the changes, Guardiola said: “It was not rotation, no. 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,” he added. “We have to be focused all the time because of distractions at Christmas time and everything that happens – you have to still be focused.”
In a separate interview, Guardiola reiterated his point about rotation having no bearing on his selection and the importance of players behaving properly.
“I didn’t rotate today,” he said. “If the players believe I rotated for that game they are mistaken. I decide the best team today for the way they play. We needed a different pace for the players and that’s why they play. I don’t know if we are going to play Leicester [on St Stephen’s Day], unfortunately they have a lot of [Covid] cases. Hopefully they are getting better.
“It depends what we see in the training sessions and it depends what we see on and off the pitch – how the players behave in this period – and I will take a decision.”
Grealish had scored only his third goal in City colours following his £100m (€117m) move from Aston Villa against Leeds, with Foden kick-starting the hammering with a goal in the eighth minute.
City’s squad were in for a recovery session the next day and had Thursday off. Guardiola was unable to take training on Friday after recording an “inconclusive” Covid test that also forced him to cancel his pre-match press conference. Subsequent tests came back negative and Guardiola took training the next day in advance of the match.
Victory over Newcastle moved City three points clear at the top of the Premier League after Liverpool and Chelsea were held to draws by Tottenham Hotspur and Wolverhampton Wanderers respectively.