The Daily Mail says Dietmar Hamann and Michael Ball were ordered to play for Manchester City's reserves on Tuesday night against Bolton after ignoring instructions to prepare to come on as substitutes at Hull City.
Manager Hughes is furious with the pair and has yet to decide on further disciplinary action, following his crackdown on Jo and Elano.
Sources at Hull said they were shocked when they observed the incident midway through the second half, but Hamann and Ball have yet to apologise for their behaviour.
Ball has not played a first-team game for City since the Carling Cup defeat at Brighton but he was recalled to the bench for Sunday's match.
Hamann's attitude is also a problem for Hughes, but it is understood that the German is claiming he did not hear the instructions to warm up.