ALAN Dunne admitted Millwall's tactics backfired after they suffered a heavy 5-1 defeat at the hands of Middlesbrough.
Dunne branded the scoreline "unacceptable" and said the Lions are unlikely to start another game playing 3-5-2, a formation which Boro ruthlessly exposed in the first half.
They were 4-0 up before the interval, with Jelle Vossen scoring a 23-minute hat trick.
Scott McDonald pulled one back after the break but the visitors underlined their complete dominance by adding a fifth goal 60 seconds later.
And Dunne said afterwards: "It's disappointing – unacceptable. We tried a formation that we've not tried before. We'd only worked on it for two days and it didn't work.
"It backfired and it wasn't for us. We'll move on from that and I don't think we'll be playing it again.
"We were trying something different and thought that with Andy Wilkinson coming back we could try with three centre halves and two wing backs
"We thought it might give us something different because we've been finishing games that way of late and doing well.
"I think it works when it's off the cuff but when we actually work on it and it's structured, it isn't the same.
"In our last three or four games we finished with a 3-5-2 but again it was off the cuff and it worked for us and got us back into things.
"On Saturday we started with it and it backfired. I think that's twice we've played 3-5-2 now and lost: today and against Birmingham last year. Both games we got beat.
"It's something we tired. We learn from it and move on.
"People have been crying out for us to play that way for a while but a flat back four would probably have been better – we might have been more confident with that.
"We're still trying to find our best team at the moment; you need a settled back four in this league and I think that's what we're hoping to have very soon."
Saturday's result continued a trend of heavy home defeats in recent seasons. Derby scored five at The Den in 2013-14, as did Peterborough the year before.
"We have one of these a year," added Dunne. "This is our one for the year. I can guarantee it won't happen again and we won't concede five again.
"In the last 10 years I've been here I think we've had one result like this a year. I don't know what happens but it's just one of those things that seems to fall into place.
"Yes, it's unacceptable and yes it's not right but we have to move on from it.
"We have got another game on Friday [away at Brighton] and if we win that we will go 16th. That's how easily things can change in this league.
"I don't think it's a crisis at all, it's just something we tried and it didn't work. The Den is a tough place to play and this shows that we have to be at our best to play at this place.
"Boro were very good. Their movement up front was very good and their movement hurt us, but I think tactically we might have just got it wrong at the back.
"The early goal was always going to make it hard. But Middlesbrough were a very good side, well organised by a foreign coach and you can see that they had talent in their team."
Asked what manager Ian Holloway had said in the dressing room after the game, Dunne said: "He lost his rag, he went mad and he was disappointed.
"But he wants us to stick together because it's not a crisis but. The goals were disappointing and we have to eradicate them.
"He wanted us to win the second half and show some pride. We scored and they scored within 30 seconds so he was disappointed in that but we move on.
"Things can change very quickly. I know next week we will bounce back and be a different team – you won't recognise the same team next week."
Millwall's players were booed off – some of them for the first time in their careers at The Den.
"The fans just want to see you try," Dunne dded. "It didn't feel like there was that chemistry between the fans and the team.
"It was flat before the game and we didn't start well. I think there was only one tackle in the first 20 minutes and that was a foul by me.
"This is Millwall – you need to get the crowd behind very early on with tackles, headers, shots and crosses and players are only learning that and experiencing it now.
"You need to set a tempo from the off, you can't wait until you're 2-0 down to start trying to set a tempo.
"I think players are learning that it can be a tough place to play when things aren't great but there's no better place when they're behind you.
"We have to work out a formula to get them on our side early on because that chemistry’s massive at this club.
"It's still early days and we're not halfway through the season. I still think we'll finish in the top half."