Peterborough manager Darren Ferguson admitted he was "delighted" despite seeing his team's unbeaten run ended by Derby who cruised to a 3-1 victory at Pride Park.
Goals from Craig Bryson, Chris Martin and Richard Keogh put Derby in control before Grant McCann converted a penalty after goalkeeper Frank Fielding was red-carded in the 61st minute.
But Charlton's late winner against Wolves kept Peterborough out of the relegation zone on goal difference and Ferguson said: "I'm absolutely delighted. We are out of the bottom three which is the best thing that's happened all day.
"Nothing else positive did happen so it's still in our own hands with two games to go and after the start we had to the season, losing our first seven games, I would have taken that.
"Sometimes as a manager you have to hold your hands up and praise the opposition and I thought Derby were magnificent. They were outstanding and thoroughly deserved the win.
"We just didn't get out of the traps, we didn't get going really until it went to 3-1. If we play like we did here we are down, if we play like we did for the last 10 games before this we will stay up, there are no grey areas, it's black and white. I have to give the players praise for the last 10 games but we were beaten by a better team."
Derby coach Andy Garner said: "We were totally in command as soon as the first whistle went. The first 20 minutes we were absolutely superb, dominated the game and were in their half constantly.
"We didn't get the goal our play justified but we stuck at it and when it came, it was a brilliant goal, a training ground goal really. Great hold up play from Conor Sammon and a typical Craig Bryson run and a good finish."
Garner had no complaints about Fielding's sending-off and admitted: "At the time I thought his starting position was too deep and I think he hesitated which was disappointing because the last thing we wanted was a penalty and a sending off. It was a poor decision by Frank, not the referee who got it spot on."