Alex Neil labelled Preston's struggles as one of the most difficult moments of his management career following a 1-0 home loss to Luton.
Daniel Iversen's late own goal condemned North End to a fourth Championship loss in five games as a lack of creativity and confidence came back to haunt them.
A potential relegation battle now looms large with Neil fully aware that solutions are not coming easy at this stage of the season.
"I won't lie, it's probably as difficult as it's ever been for me. I've always been fighting middle to top of the table, it's tough," he said.
"People talk about knowing your best team and I used to get criticised for having my best team and playing it more often than people thought I should have.
"If I'm being brutally honest at the moment I haven't got a scooby-doo what the best team is. Because what happens is, what I get from one week to the next, God knows.
"Your best team generally, you have reliability in it. You know what you are getting week in week out. At the moment we are nowhere near that.
"There was a lack of quality, in the first half you can certainly see a lack of confidence.
"There were four or five different occasions when we could have brought the ball down and made a pass. We don't, we sort of kick the ball the way we are facing.
"The basics, at the moment, we are finding difficult and poor in general. That makes it extremely difficult to win any football match if you are not doing the basics well enough.
"It was not through lack of effort, we tried."
With seven minutes to go, Mpanzu whipped a delightful cross into the six-yard box, with Iversen making a magnificent save from a Kiernan Dewsbury-Hall diving header.
But Luton substitute James Collins reacted quickest and steered in from a tight angle, the ball going in off the unfortunate goalkeeper.
Back-to-back victories, and a first at Deepdale since 1972, takes the Hatters to 50 points – a tally they reached in the 46th and final game last season.
"We are trying to make sure we keep climbing the league," said manager Nathan Jones.
"First half was lacklustre. If we had a bit more quality, we could have created a lot more. In the second half we picked it up slightly and I felt we deserved a win.
"I felt if we had just stepped it up a little bit the game was there to be won. That is not being disrespectful in any way. We needed to up our game.
"We lacked a bit of tempo and a bit of quality. If we had that in the first half it could have been a different story.
"I felt we were the better side. Not massively but I felt we edged a real tight game and being the away side that is obviously a good performance because this is a tough place to come.
"Of course he [Collins] is claiming the goal. He had the last touch and put it in and the keeper couldn't keep it out. It is clearly his goal. I'm delighted for him, a poacher's goal."