The 65-year-old pointed to the Rs' previous positive results, such as the win over Chelsea, as reason to be positive heading into the Premier League clash at Loftus Road
The Rs are currently four points adrift at the bottom of the league following a 4-1 defeat to Swansea City last time out, but had lost just once in eight games prior to that result.
Redknapp's outfit host United on Saturday, and the boss used examples of his squad’s victory over London rivals Chelsea and draw with old club Tottenham as proof the bottom-of-the-table side are able to cause an upset at Loftus Road.
“You can’t predict results,” Redknapp told the Fulham Chronicle.
“We’re playing Chelsea away on the back of being smashed to pieces by Liverpool. What’s the score going to be you might ask? 3-0 and 4-0 to them? I was a surprised as you were.
“We then play Tottenham at home who’ve beaten everybody away and have scored in all away games, and they don’t score against us.
“Against Man City, who are champions, we get another point and then another at West Ham, which is a hard place to go.