Loftus Road will host a potentially pivotal match in the relegation battle, with Rangers seven points adrift of safety and Wigan above the bottom three on goal difference alone.
Successive defeats to Aston Villa and Fulham have left QPR in a dire position, but Redknapp wants his team to share his conviction that they can stay in the top flight.
"When I stop believing, the players will stop believing. If I send out the wrong message they'll down tools, thinking we've had it," he said.
"I don't feel we've had it. I couldn't tell you the pleasure keeping QPR up would give me. It would be fantastic.
"We have to keep going - we've got to beat Wigan. There's nothing else for it, we have to beat them.
"Nothing else but a win would be any good to us. We need to win and keep winning. We need to win four or five games - it's a tall order but not impossible.
"But if we don't win on Sunday we won't give up because there'll be six games left and we could still win all six. You don't give up, you have to keep going."