Carroll missed the first half of the season due to injury, but Downing believes that the striker is unique enough to persuade Roy Hodgson to take him to Brazil this summer.
"He knows that Roy Hodgson is a big fan of his and I think if he stays fit, even if he didn't score between now and the end of the season, I still think he is a big threat for England and I think he will probably take him," the Hammers winger told members of the media.
"That is my own opinion. I just think he needs to keep playing well and take his good form into the World Cup.
"If you put it in that area, he gets on the end of it. He is a target to hit. I think he is in with a hell of a chance of going."
Carroll has not played for England since October 2012.