Robbie Neilson admitted it was the most disappointing defeat since he took over as MK Dons boss last December after losing 4-1 to Blackburn Rovers on Saturday.
Trailing after just 90 seconds, Dons got back in it through Ed Upson midway through the first half, but two Charlie Mulgrew goals and another from Dominic Samuel completed Rovers' rout.
Dons form on the road has been poor since Neilson took over - picking up just five wins in 18 outings - and the Ewood Park thumping is the worst during his time at the club, equal to the 4-1 defeat at Huish Park against Yeovil in his first game in charge.
"Probably," said Neilson when asked if it was the most disappointed he's been after a Dons game. "We came up here and were positive about what we wanted to do and were confident we could get something from the game.
"I thought we were poor today. We came here with a game plan, but after 90 seconds we were a goal down, and we're battling against it after that.
"But in the first 10 minutes we were poor, but we managed to get a foothold back in the game. Then in the second half, we looked better but were 2-1 down, but it was a poor set piece goal to concede and after that we were chasing our tails.
"All in all, it wasn't good enough. We need to be better. For a lot of the game today, we were caught in two minds. We didn't give ourselves enough of a chance, our decision making was poor, and I think our work rate was poor too, which for me was unacceptable.
"It was just the basics that went wrong today. We can talk about not gelling all we want, but if you can't pick the right pass, or make the right touch, it doesn't matter who you're playing with - you best mate or someone you've never met before. The standard wasn't good enough today, we've spoken about it at length and we all agreed."
Despite picking up just three points from a possible 12 so far this season, losing three and scoring just twice, Neilson still believes his side is capable of fighting for promotion and insists there is no reason to hit the panic button yet.
He said: "We can compete in League 1, and today was a tough day. Blackburn have come down from the Championship and have a huge budget compared to ours but we are still a strong League 1 team. We don't want to get carried away but there are basic things we have to get better.
"The belief simply wasn't there. There are good players in that dressing room but we have ot add to it and get our lads back from injury. I still believe we have a very good team here, we just need to get ourselves together."