The Spurs winger was initially sidlined with a groin injury sustained at the end of December and looked ready for a return to action last month.
However, he aggravated the injury during training last month and could now be sidelined for the remainder of the season.
"It must be frustrating for Aaron," Redknapp said.
"He's desperate to get fit. We just can't get him right. He's had a few goes and broken down.
"He's been back to the specialist.
"We're taking our time again, building up his strength in the groin area.
"He works every day with the physios and hopefully he will be working back outside shortly, but he's not ready to join the group again. He's quite a way off.
"I hope he'll play for us before the end of the season.
"He could suddenly see a bit of light and come back and if he does then he could be ready.
"Four or five weeks, we'll have to wait and see."