Club owner Randy Lerner is an admirer of former Chelsea boss Carlo Ancelotti but the Italian's announcement that he plans to take a year's sabbatical from the game has scuppered any hope of him taking charge at Villa Park.
Mark Hughes was the odds-on favourite with the bookmakers after quitting Fulham but Villa insisted the timing of his departure and their own vacancy becoming available was pure coincidence.
Former England coach Steve McClaren, one-time Tottenham boss Martin Jol and Bolton manager Owen Coyle are believed to be among the candidates under consideration, but sources close to the club have indicated to Press Association Sport that there is nothing imminent on the horizon.
It could be the end of this week or even into next week before there are any developments.
Villa striker Darren Bent admits the players have no idea who will replace Houllier after he stood down for health reasons, but the England international believes the Villa fans will give the new man time to stamp his mark on the club.
Bent said: "Every day I am checking on television and speaking to people to see who it's going to be be but you just don't know.
"Mark Hughes was supposed to be in the running but he has gone out now and I couldn't tell you who it's going to be. I couldn't even tell you who is in the frame now because it's so up in the air.
"But I'm sure, whoever the new manager, the fans will give him time. It's a big, big job to take and I'm sure the fans will be behind him whoever he is.
"It's been a difficult season, but we still finished ninth and we need to build on that."
Source: PA
Source: PA