The talented 20-year-old was benched for the Reds' 5-0 defeat at Burnley on Saturday, with Davies only allowing him a late cameo at Turf Moor.
The Forest boss believes the midfielder is overweight and has questioned the lifestyle led by certain members of his squad.
It is a problem Davies could do without as Forest continue to languish towards the foot of the Championship, but he is determined to stand his
"I had to drop McGugan again because his off-the-field discipline is not
what it should be," the Scottish coach told the Nottingham Evening Post.
"I am not going to get into details. But there is a situation, not just
with Lewis, but with one or two of them, with regard to their lifestyle, eating habits and preparation.
"There are one or two players in the squad at the minute that we should be leaving out, sending them away for a while so they understand things.
"You can do that in a winning side but at the moment there is a collective responsibility to get us out of the situation we are in."
Davies has also apologised to the Forest faithful for the shambolic
weekend showing against the Clarets.
"These fans have been fantastic, we owe them a huge apology," he said.
"We will get some work done during the international break. But most of our work needs to be done in our heads. The goals we are conceding are in our heads at the minute.
"It is not physical, it is not a lack of skill, it is in the head. That is what we have to try to work out."
Coca Cola Ch'ship Relegation 08/09 Win Outright: Notts Forest 9/4