Rangers remain nine points adrift of Burnley in second following a 2-0 defeat at Brighton on Tuesday night.
Goals from Leonardo Ulloa and Stephen Ward in the final 13 minutes condemned Rangers to a fourth defeat in their last six matches.
But R's manager Redknapp insisted: "We've got to keep going. It's going to be hard but it can happen."
With two of the Sky Bet Championship's meanest defences taking on two of the meekest attacks, a stalemate always looked on the cards at the Amex Stadium.
That was until the 77th minute when Argentinian striker Ulloa pounced for his sixth goal in eight matches.
Brighton right-back Bruno made a rare foray forward and his low cross was turned in by Ulloa at the far post.
And eight minutes later full-back Ward tapped in the killer second from Kazenga LuaLua's corner to make it 2-0.
Prior to that Brighton had barely registered a shot on target while Seagulls goalkeeper Tomasz Kuszczak made fine saves from Ravel Morrison, Junior Hoilett and Armand Traore.
"It was very frustrating," added Redknapp. "I thought we were just waiting for a goal to come.
"We had all the play, all the chances. We were strong at the back, good in midfield, making chances, but we just couldn't score.
"I thought it would be a hard game but it wasn't, even though we lost.
"I couldn't moan at them, I thought they were excellent for 80 minutes and we got done against the run of play.
"Our keeper had not had a shot to save, then suddenly you're one down. But that's football. It happens."
While Redknapp is eager to avoid the play-offs Brighton are desperate to be involved.
A fourth win in six matches lifted Oscar Garcia's side up to seventh, two points behind Reading in the final play-off spot.
"I am extremely proud of my players and their performance against Premier League-quality opposition," said the Seagulls boss.
"But I don't think it was our best performance. They have a fantastic manager and fantastic players but we have played better than this and lost.
"We knew we would find more space in the second half. And after the first goal we kept going and we didn't sit back.
"Leo scored another crucial goal for us. He has the desire to score and wants to get in the box - and his desire made the difference."