The Football Association wrote to Mancini following his claim that "maybe the referee ate too much for Christmas" after Friend missed what the City boss felt was a clear foul on Pablo Zabaleta in the build-up to Adam Johnson's winner.
Although over a week has now passed since the incident, the judicial panel granted Mancini's request for an extension due to the demands placed upon him during the packed festive period.
It is thought Mancini is facing either a warning or a fine for his reaction, although the disciplinary panel do have the option of a touchline ban should they wish.
Whilst City have made their irritation known at their manager being investigated whilst Sir Alex Ferguson escaped without punishment for his behaviour during Manchester United's win over Newcastle the same day, it has been pointed out by the FA that there are clear differences.
The main one is that as Mancini delivered his assessment after the game and Friend was not present - unlike Mike Dean, who described his own clash with Ferguson before the second half of United's 4-3 victory as 'cordial'.
In addition, whilst Mancini's comments could be viewed as an amusing aside, they have called into question Friend's competence which the FA, at the very least, feel demands clarification.
Source: Manchester City MAD