The Lilywhites are four points off the play-offs and down to ninth place after successive home defeats to the Rams and Cardiff - both of who have leapfrogged them.
With only six games to go, it would take a huge swing in form for North End to get back into the play-off zone.
They are six matches without a victory and have won only one in eight - not the sign of a top-six chasing side.
In the defeat to Derby, Neil's men had 54% of possession but didn't really lay a glove on the Rams.
Of the nine shots they had in the game, only one was on target - Brad Potts shooting straight at the keeper in the second half.
PNE manager Neil said: "In the second half we were right on top of the game.
"The subs made an impact but for the all the possession and control of the game we had, we couldn't find that little bit of magic to get the next goal.
"Derby sat in banks when we were in control and we put some great balls into the box.
"We put as many forwards on as possible, we took Ben Pearson off to try and force the issue with another attacker.
"It was really frustrating that we couldn't get that clear-cut chance."
Wayne Rooney settled the game in Derby's favour with a free-kick in the 18th minute, Paul Huntington having been penalised for a foul on Louie Sibley.
Neil said: "In the first half I think we struggled with their passing in terms of locking them in.
"I didn't think it was a foul leading to the goal. Hunts just comes across and leans him out of the way.
"Wayne Rooney then produced a bit of quality.
"After that we got ourselves back into the game, we had a chance soon after with Alan Browne.
"In the second half we were much improved."