The striker was omitted from Roy Hodgson's 30-man squad to take on Denmark this week, but the West Ham boss is convinced he will go to Brazil.
The striker's campaign has been blighted by injury, while a three-match suspension for elbowing Swansea City's Chico Flores saw him make just his first appearance in a month in Saturday's 1-0 defeat at Everton.
But, with a fortnight until West Ham's next fixture, Allardyce is hopeful the former Newcastle and Liverpool striker can return to full fitness and become part of Roy Hodgson's England plans for the World Cup.
"I think Andy is a fantastic alternative in so much as you can change from the plan that you've got, whether you start with him or bring him off the bench," he told reporters. "I'm not talking about pumping the ball up to his head. I don't put him on to just win headers but to control the ball with his chest and feet and bring other people into play.
"You saw on Saturday what he can do inside and outside the box. If he stays fit, he's got it in his own hands and if he does as well as he did last season, Roy can't ignore him."
Allardyce also revealed he is considering organizing a friendly match for next weekend to help build Carroll's fitness.
"Andy has been constant in training terms but it's match fitness that we need to help him with," he said. "If anybody needed a game next week it would be Andy, but we've got to wait a couple of weeks before we can get him fit again.
"We may fit in a behind-closed-doors game for him and some of the other squad players that might not have been playing so much recently."
England meets Denmark in an international friendly Wednesday.