Saturday's 3-2 defeat to relegation rivals Aston Villa leaves the West London club rooted to the bottom of the Premier League, seven points adrift of safety.
QPR have won just twice away from home this season and Redknapp believes that his side must start pick up more points on the road if they are to avoid relegation.
"We have to win at Fulham or Reading and win our home games. If we do that, we can still stay up," ESPN quotes Redknapp as saying.
"It was always going to be hard [staying up] but we're playing well," he said. "In the first half, I couldn't have asked for more and, all through the game, we had chances.
"This is probably tougher than it was at Portsmouth but we're playing well. That's the key."
QPR face Fulham on March 30.