Jamie McAllister is the only recognised senior left-back at Ashton Gate. Liam Fontaine and Lewin Nyatanga can play in that position but both are centre-halves by trade.
Millen also wants a creative midfielder in the mould of Paul Hartley. The Scotland international left City to join Aberdeen in the summer and has not been replaced.
"My need is for a natural left-footer who can get up and down the pitch," Millen told the Bristol Post. "Jamie McAllister has done an excellent job for this football club in recent seasons, but he cannot be expected to do it all on his own. We need another natural left-back to provide competition and cover and that will be my priority when January comes.
"We didn't want to lose Paul Hartley but he was determined to leave. He told us on the first day of pre-season and there was nothing we could do to change his mind.
"He was the kind of player who could pick out a defence-splitting pass and, although we have other progressive midfielders, we still don't have anyone quite in that mould. I'd like to bring in a creative midfielder if I can and, in my own mind, I know what I want."
Source: PA
Source: PA