Manager Simon Grayson felt that key moments in today's 3-0 defeat cost them at Elland Road.
Goals from Pablo Hernandez, Kemar Roofe and Souleymane Doukara condemned the Lilywhites to a first defeat in five games.
"Key moments in key parts of the game can win and lose you games and I thought that today," said the manager on today's defeat.
"We started the game really well and had some great opportunities to win the game and go in front but then we make a real bad defensive error. Leeds didn't give us too many problems, we just didn't take too many chances and then that gives them a big lift.
"We've had some great chances to get back into the game and get something out of the game but we've gifted them three chances and they've taken them and we've not defended well enough.
Moments in the game included an early chance for Tom Barkhuizen which could have given the Lilywhites the lead, and the initiative to win the game and Alex Baptiste's red card five minutes from time just as North End were pushing for a way back into the game.
"I didn't see the sending off and I'm as surprised as anybody," he continued. "Baps' doesn't think it's a sending off - I'm not sure, I'll have to speak to people and see the report.
"We didn't do enough in both boxes and that's what wins you football games. We played well at times, we just didn't do what was required to win the match and when you're defending against a team like Leeds you have to be strong and disciplined in every aspect of the game and we didn't deal with them well enough in the game, more mentally than anyone else."
"You have to limit the opportunities to teams who are playing in front of big crowds so that they can get frustrated but we didn't do that from 15 minutes onward and allowed them too many opportunities."
"Defensively, we were as poor as we have been all season and when you look at the goals, they were big mistakes from three experienced players.
Grayson and his charges now have just under a week to prepare for the next game against promotion chasing Huddersfield Town on Friday before welcoming Norwich City to Deepdale on the Monday, and the PNE gaffer believes his side can't afford to lull on today's game.
"We knew that games coming up are tough games but we've got to do better at both boxes. I don't think anybody could say that Leeds were very good today and that they deserved to win by three goals but they took their chances and defended when they needed to."