Alex McLeish has been promised funds of up to £40million to spend by new owner Carson Yeung when the window opens and vice-chairman Yu is not ruling out the possibility that up to five new players could be signed by the Blues boss next month.
"Our priority now is to strengthen the team and make sure it stays in the Premier League," Yu has told the Birmingham Mail.
"By the end of January, you never know. It could be that something unexpected has happened. We will do what we can do.
"Carson Yeung is preparing to splash the cash so we can't say 'no', we can't say 'yes' (to spending big money on oneplayer).
"But if a top-class player who is really keen because they know we are going forward, came over to us and talked, and we were sure their attitude was right, everything was right, even if they were expensive, we might concede that we need them as well.
"Our door is always open. First and foremost, everything that will be done will be done with the best interests of the club in mind.
"It doesn't matter what positions players are, what sort of conditions they are asking for, as long as they are right. That's the main thing.
"It's no point buying someone who is cheap or is expensive if they are not going to fit in.
"As for how many players, we totally understand that if it means two, three, four - even five - that it is not an issue. If they have ability, quality, the character and attitude - that's what counts.