Walker looked a certainty to go to Brazil as Hodgson's first-choice right-back following a series of impressive displays earlier this season when Liverpool's Glen Johnson was out through injury.
But the Spurs star suffered a pelvic injury during Tottenham's defeat to Benfica seven weeks ago - and he has not played since.
Spurs have told Hodgson that Walker has had an injection to try to help his rehabilitation, but it may be too late for the former Sheffield United right-back.
"We haven't been told for certain that he will be out for the next six to 10 weeks but we are concerned that it has been a long time he has been out," said Hodgson.
"During that time he has not been able to do any training with the rest of the team as far as I know.
"I know he has had another injection. We are waiting to find out whether that helps. He has not been fit for a long time."
Should Walker miss out on the World Cup, Hodgson may turn to Liverpool's uncapped full-back Jon Flanagan, who has turned in a series of mature displays this season.