Day is currently sidelined with an ankle problem but is set to play in the club's reserve side in the next two weeks.
Ferguson told the Peterborough Evening Post: "Jamie is very much part of our plans.
"I have always liked him as a player and I certainly think he will cope in the Championship.
"It is not unusual to pick up a little injury and being out for so long but Jamie is ready for games in the reserves and he will be back in the squad in a couple of weeks' time."
Source: Team_Talk