Shaun Wane struggled to hide his disappointment after Wigan surrendered their golden home run in “a cheap way”.
Widnes pulled clear at the top of the table with a deserved 18-12 victory.
It was the Warriors’ first Super League defeat at home in 21 months - and the loss denied them their best ever start in the summer era.
Wigan matched the visitors for tries scored but with no conversions, Rhys Hanbury’s three goals proved decisive.
Wane admitted the Vikings deserved the two points.
He said: “We went away from our system which is disappointing.
“Our good record here… that’s gone, and it’s gone in a cheap way.
“The tries they scored weren’t from miracle plays, they were from us going away from our system.
“If we’d have just been a little bit smarter we’d have got the game but in the end the best team won.
“Credit to Widnes, they were good for the win. They are the best team in the comp’ and if you give them cheap field position, those defensive errors are going to burn you and they did - it’s sad.”
Wigan had led 8-0 at half-time courtesy of a long-range Liam Farrell effort and the first of Josh Charnley’s two tries.
The winger’s second helped them into a 12-6 lead but two Vikings tries in three minutes turned the game on its head.
Coach Denis Betts, a Wigan legend, said: “There are a lot of ex-Wigan players in the group and there’s emotion in the side and that burns energy quickly.
“We looked shot after 20 minutes but we are a fit team. We came back in at half-time, took the emotion out the game and did what we needed to do.
“It’s hard not to say it’s a fantastic night for the club, for the players. We’ve had some tough days here. We’ve had a couple of floggings here over the years and some tough experiences.”
Wigan - still missing five internationals - now have a week to prepare for their next game, a mouth-watering derby at St Helens on Good Friday.