Aidy Boothroyd was unhappy after watching his Northampton side ship a last-gasp goal to lose 1-0 at Plymouth on Saturday.
Striker Reuben Reid helped on Luke Young's defence-splitting pass to enable livewire Lewis Alessandra to beat the offside trap and deftly slide the ball past Town's busy goalkeeper Matt Duke, who had gone full stretch to deny the attacking midfielder minutes before.
"There's no better victory than that one in the 90th minute because you know that you are home and dry, barring a miracle, and there's no worse loss," Boothroyd said.
"It's our own doing, it's our choice to concede late goals. It's very irritating from my point of view, it's not acceptable and clearly I need to make some changes.
"I am really, really irritated by what I have seen in that last five minutes. It's not good enough.
"You want to win games, you want to be successful, whatever you do, you do not concede in the last five minutes.
"There's no point in doing half a job. There's no point in turning up, preparing like we do, coming down here overnight, working hard all week to get a result and then throwing it all out the window because we are not disciplined enough to win a game.
"There's clearly lots of work to be done but also changes that need to be made.
"I don't work and come into football to get beaten in the last minute and neither does anybody else but it is very important to recognise that we did really well for long periods of the game, stuck to the game plan - just like Rochdale - and just got done because of our lack of discipline."