Tuesday's 2-0 defeat at Blackburn left Rangers 13 points behind second-placed Burnley with just 15 to play for.
Crucially, they are still nine points ahead of seventh-placed Brighton, but Redknapp knows a run of three games without a win is not the sort of form to take into the play-offs.
"We need a result and quickly," said the Rangers boss.
"We're still missing five or six players and that's really hurting us. We just need to get a result or two to get us into the play-offs.
"We're focused on making the play-offs now. We've got a big cushion but we need to go on a run to make sure we're heading into the play-offs with momentum."
Redknapp hopes to have Joey Barton, Clint Hill, Jermaine Jenas and Nedum Onuoha back from injuries when Rangers host Nottingham Forest on Saturday.