Milan's players slept at their training centre overnight on Saturday and will remain at Milanello indefinitely following their 2-1 defeat to Udinese.
Filippo Inzaghi saw his side dispatched with relative ease at the Friuli - Giampaolo Pazzini's late consolation adding a touch of respectability to the scoreline.
However, former Milan striker Inzaghi was unhappy at the attitude of his side, with the club stating the 'retiro' would go on indefinitely ahead of Wednesday's visit of Genoa.
"The attitude was wrong and so was the way we approached the match," Inzaghi told reporters on Saturday.
"We deserved to lose. There are very few excuses and the only thing to do now is to roll up our sleeves and do well in the last six matches, because we're Milan and our dignity is involved.
"We will stay at Milanello, [Sunday] morning we will have training and then together with the club we will take a decision [over a training retreat].
"I have an idea and I will share it with the club. When you hit the bottom you need to reflect.
"It isn't a retreat of one or two days that changes things. If the attitude is wrong and you are not focused out on the pitch, it is hard to get back into a match.
"With the attitude showed we would have lost to whoever."
Milan sit 10th going into their final six games and appear set to finish outside the European places as well as below rivals Inter.