Assistant boss McAllister will be in charge of Saturday's home Barclays Premier League clash with Stoke while Houllier remains in hospital after suffering chest pains on Wednesday.
McAllister, who was a player at Liverpool when Houllier underwent heart surgery a decade ago and initially feared the worst after hearing of his current plight, said: "I think he will be back, most definitely, knowing the guy. We're only two days away from it happening (having chest pains) and I've had three teams texted to my phone. He's organised training for the last two days so his mind is on the job."
He added: "People ask why he should want to carry on at his age (63) but you could level the same question at Sir Alex Ferguson, Arsene Wenger and Roy Hodgson.
"These guys are madly, deeply in love with the game and they cannot go without it. It's simple. They're living through the game.
"Maybe they didn't get the success as a player but, when they've moved to the managerial side, they're living that life of not being top players through the management side."
However, McAllister also knows it is crucial Houllier listens to the advice of the specialists before returning to Villa.
He was back at work within five months at Liverpool in 2001 when in a far worst state health-wise than now.
McAllister said: "I think this time is definitely going to be dictated by the doctors and the specialist. It cannot be the gaffer's decision or anyone at Aston Villa.
"It's got to be the doctors and the people at the hospital who tell him when he's ready to go back. He would be foolish to not listen to these people. I think that's the big thing."
Source: PA
Source: PA