Pep Guardiola tore into Leroy Sane during a furious dressing down at half-time of Manchester City's FA Cup defeat by Wigan last week.
Sources said that Sane's City teammates were left in stunned silence as Guardiola accused the winger of failing to pull his weight and not adhering to his instructions in the first half of the 1-0 loss.
The anger extended to the City manager substituting Sane at half-time.
The Catalan was already irate before he entered the dressing room after angry confrontations with Wigan manager Paul Cook in the wake of City defender Fabian Delph's red card.
The mood darkened further when he turned on Sane, with one source claiming the manager's dismay could be heard in the corridor outside the dressing room, although the matter was considered dealt with at the time.
Sane was back in the starting eleven for City's 3-0 Carabao Cup final triumph over Arsenal at Wembley on Sunday, with Guardiola confident that his message has got through to the German.