"In eight days' time we are able to use the emergency loan market so there's no need to rush," Millen told the club website.
"There are still a few things ongoing and a couple of deals are possible when we can loan again."
Millen added: "Another factor is the Premier League clubs name their squads tomorrow [Wednesday].
"We may know more about who is available to loan in from the publication of the top flight squads."
City boosted their striker force last week with the double-signing Brett Pitman and Jon Stead who both made their full debuts in the 2-0 defeat to Ipswich on Saturday.
Source: BBC Sport
Source: BBC Sport