Paul Furlongs goal had given the home side a worthy 1-0 half time lead but a better performance after the break by North End saw goals from David Nugent and Chris Lucketti earn the Whites all three points which took them into fourth place in the Championship table.
Davies said: "We were very poor in the first half and we let down the fans with that performance.
"QPR deserved to be ahead and there were one or two choice words at half time. There were just a lot of disappointing performances.
"I am very pleased with the three points but we are not getting ahead of ourselves. There are a lot of points we can improve on and we are a mile away from being the finished article.
"I keep saying to the players there is nothing to celebrate now. We can look back at the end of the season."