A goalless draw with Reading earlier today ensured that the Loftus Road side will be playing in the Championship next season.
The QPR manager told Sky Sports News: "There's a lot of work to be done next year and it will be very difficult to get promoted. There are some good teams in the Championship.
"The first thing I said to them is we have to come back in pre-season and get super fit because the Championship is Saturday-midweek, Saturday-midweek and if you're not fit enough to go the pace, you won't survive and you won't get out of that league.
"It will be a big challenge. There are lots of good teams and massive clubs. There are big clubs who have all been in the Premier League before and we are just one of them. We will do our best next year to try to get up, but we are going to have to work very, very, very hard in the summer, during pre-season and certainly during next season to try to achieve that."
Today's result also sealed Reading's relegation from the top flight.