The new Rangers boss took charge of his first home game on Saturday and saw his side hit the woodwork twice in a 1-1 draw with fellow-strugglers Aston Villa.
It was an encouraging display from the west Londoners, but they remain rock bottom with no wins from their first 15 league games, equalling the unwanted record set by Swindon in the 1993/94 season.
"I think December is decisive," Redknapp said. "You've got to see where you are then, haven't you?
"If you're in touch, we can get a couple of wins and keep ourselves in there, then great, have a go.
"If not, you've got to be careful. We've got to look at it and see where we are.
"Hopefully we are in touching distance and can get a couple of players in that can make the difference and get out of it that way."
Redknapp added: "At the moment, I've got what I've got and we've got to get out of it with this lot.
"We've got to close the gap, get ourselves within at least touching distance of fourth from bottom and if we can do that I am sure we will have a go in January."