The West London side were held to a 1-1 draw with United at Loftus Road on Saturday, but were unlucky not to take all three points from the game with Steed Malbranque seeing his late penalty saved by Fabien Barthez.
United are currently trailing top two Liverpool and Arsenal in the league sitting in fourth spot and England Under-21 international Knight believes teams no longer fear facing Sir Alex Ferguson's troops.
"Teams definitely don't fear United like they used to," said Knight. "They've not had the best of starts this season and teams are going to capitalise on that.
"Looking at the players they had missing, we feel we should have got all three points."
