Grimsby Town ensured Dover’s long trip to Lincolnshire was as miserable as the weather at a rain-soaked Blundell Park.
Manager Andy Hessenthaler’s side was 5-0 down at half-time before the table-topping hosts added a sixth with 20 minutes to play.
Hessenthaler labelled the performance as “unacceptable”.
He said those 60 plus Dover fans who made the 475-mile round trip didn’t deserve to see that.
“Let me start by saying that I thought that it was an absolutely outstanding effort by our fans who made the long journey and who, in truly horrendous conditions, stayed to the bitter end and clapped the players at the final whistle.
“That’s true fans for you and believe me, we owe them and every other Dover fan for what we produced on the day.
“The way we lost the game was unacceptable and we should all be hurting after it.”
Although the final scoreline doesn’t suggest it, it was Dover who started the better of the two teams in front of the near 6,000 strong crowd.
Hessenthaler said: “I said before the game we needed to start well and silence the crowd and we did for the first 15 minutes or so.
“We played some positive football and created some decent chances and they (the crowd) were quiet.
“However, that changed when Harry (Ransom) was booked and they were calling for him to be sent off – that changed the tempo of the game.
“It was like waving a red flag at a bull – they came charging at us and we couldn’t handle it and once we conceded that second goal, our heads dropped and we cannot afford to do that.
“The gulf in the size of the clubs really showed and they looked fitter and sharper than us, but as a group, we made too many errors defensively through a lack of experience and naivety.
“We’ve got to keep fighting, but on Saturday we didn’t show anywhere near enough fight against a massive club in this division.”
The manager also named Yannis Drais on the bench for the first time.
The 27-year-old French midfielder, who will wear the number 31 shirt, made his debut as a second-half substitute, replacing Da Costa as Hess changed shape.
Drais arrived on non-contract late last week after training with the side for a couple of weeks.
Hess said: “We are lacking central midfielders with Ryan Hanson out injured and he’s looked OK in training, so we’ll see how it goes.”