The veteran midfielder, who signed a one-month deal with the Lions on Friday, claims that a lack of effort was to blame for QPR being relegated from the Premier League last season.
"Did those players earn their money last season? No, of course they didn't. Definitely not.
"I've been in the game for 20 years and I can tell when players are fighting for the cause and when they are winging it."
Derry joined QPR from Crystal Palace in 2010.