Shaun Wane was “hurting” after watching his Wigan team crash 42-30 to Wakefield - despite taking a 20-0 lead.
A whirlwind opening featuring a try for teenage debutant James Worthington had put the Warriors well in control.
Wigan teams should never be giving up a 20-0 lead, no matter whatShaun Wane
But the visitors turned the game on its head, scoring the next seven tries - including a Bill Tupou hat-trick - to snatch their first win at Wigan in eight years.
And Wane said: “Wigan teams should never be giving up a 20-0 lead, no matter what. There are no excuses from us.
“But my memory is good, we did a great job against St Helens but we just couldn’t back it up.
“I’m disappointed with how we’ve defended, we showed some softness.
“We fell apart, missed too many one-on-ones and put ourselves under pressure.
“They were the best team, they’re a big, big team. We went into it lethargic.
“We had a game plan to win and we didn’t stick to it for long enough, and I need to look at the reasons why, and they’re simple things.”
Sixth-placed Wigan have not won in five Super League matches and are four points outside the top-four places - putting a greater emphasis on Saturday’s game at Hull FC, who are fifth with 19 points.
Asked whether their run without a victory had created any nervousness, Wane said: “There’s absolutely none from me - I’d be disappointed if there was any from the players.
“We’ve got a month on the road. I’m hurting, I’m sure Lee Radford is hurting, and I’m looking forward to Saturday.”
One positive to come from the Bank Holiday Monday fixture - watched by 13,110 fans - was a two-try debut from centre Worthington, just a week after his 18th birthday.
He got his chance after Joel Tomkins, Liam Forsyth and Joe Burgess joined starting centres Anthony Gelling and Oliver GIldart on the sidelines, taking the total of missing frontline players to 10.
“He did good,” said Wane. “He’s a Wigan kid debuting at home, to score on his first touch is fantastic, and I’m disappointed for him we didn’t get the win.”
Wakefield have now moved level with Leeds into fourth-spot after six straight wins.
Trinity coach Chris Chester said: “We’ve been on the end of some big scores here. To come and get ourselves in the game shows how far we’ve come as a group. We can challenge anyone at our best.
“I’m really pleased we got back into the game and got a massive result for our club.”
Wane said there was a chance Tomkins and Burgess may return this week.