Redknapp maintained Spurs would take no risks with Lennon's rehabilitation and Press Association Sport says Spurs will be seeking further specialist advice on how best to manage the injury to ensure a proper recovery.
"I am optimistic, but it just seems to have dragged on," said Redknapp. "At first we thought it would be four or five weeks maximum and we were hoping to get him back for the Leeds game at home.
"That was five weeks ago.
"It has gone on from there really. Until he actually gets fit, we will just have to wait and see."