Redknapp, who replaced Mark Hughes in November, warned life in the npower Championship will not be a bed of roses.
"It's been a miserable season," the QPR manager said.
"Something has got to be done because if you take that team out there at the start of next season we wouldn't finish in the top half of the Championship.
"We haven't got the quality in my opinion, we're short of good players who can really play at the top level.
"We're going to have to do something about it. It's going to be a very difficult job."