What on earth did we have here, the dawn of a brave new world for top-flight English football or a day when plutocrats like John Terry and Didier Drogba exhausted most of their urgency getting out of bed? The statistics imply heavily the latter, this being Wigan's first win over a top-four club in 35 attempts, but you accept them only at the cost of disservice to the excellent performance of Roberto Martinez's team.
Unfortunately, there is no way around it. Chelsea were simply not recognisable as the force who since the start of the new season had been defining with cruel efficiency the difference between hope and reality. If you didn't know better, you might have thought they had been celebrating somebody's birthday.
They seemed to have slowed down a yard a man after an initial flurry which promised the full ration of mayhem. Chelsea are nothing if not relentless, so it meant that they were pretty much nothing.
However, on another day and in another place they might have got away with it. When Drogba saw his shot sneak through the legs of goalkeeper Chris Kirkland for an equaliser early in the second half, some heavyweight verities appeared to be back in place.
Chelsea would simply grind down Wigan's impertinence, just as the power of Manchester United and the beauty of Arsenal had broken their resolve so profoundly in recent weeks.
There was, though, a significant new difference. Wigan had been persuaded that they could still compete, that the power and the panache of their new leader, Hugo Rodallega, had not been an illusion, no more than that distinct impression that Chelsea were deeply at odds with themselves.
The result was that no single piece of football iconoclasm ever had a more potentially inspiring explanation than the one provided by the victorious Martinez.
Wigan's Spanish manager said: "You can see we've learnt our lessons from the past. Many times we have played against the top four and it's just a damage limitation performance.
"You're hoping for a performance and we've always been brave. If you're not brave enough you get punished as we saw against Manchester United and Arsenal. The only way we could beat Chelsea was if we were big enough to learn our lessons and the players did that from the first minute.
"There was no fear, there was a huge belief in what we were doing. Even when we conceded, which has been a problem in the past, we carried on doing our jobs and kept our standards."
According to Martinez, Wigan's problem in the past had been a mental block "in terms of hoping for a win and fearing the worst".
For Carlo Ancelotti the end of his perfect introduction to English football was accompanied by one of the oldest truths: "It is impossible that all our matches will be good. The first 10 minutes were very good and maybe we thought it was an easy game. Instead, Wigan played very well."
They did indeed, but well enough to win if Chelsea had not departed so far from their normal standards, if even Michael Essien at times had looked less than a huge force of nature and Terry and Ricardo Carvalho at several critical points appeared to be in need of some formal reintroduction?
It is no insult to the splendid aggression of Rodallega and his upwardly mobile partner at the front, Jason Scotland, and team-mates who never ceased to believe in their own possibilities, to react to the question with some scepticism. Petr Cech's red card and concession of a penalty – over which his lengthy protests to referee Phil Dowd were not the least bewildering aspects of an extraordinary day – were pivotal but Martinez was surely right to say that the meanings of victory and defeat lay elsewhere.
The most plausible one, unquestionably, rested midway between Wigan's self-belief and Chelsea's near total failure to perform adequately.
Injuries to Ashley Cole, who limped out of the stadium heavily, and John Obi Mikel, were other reasons to provide Ancelotti with a less than carefree journey home as he contemplated his first collision with the elite of the Premier League when Liverpool visit Stamford Bridge next weekend.
There's nothing like a pummelling at somewhere like Wigan, and a few injuries, to concentrate the mind on such problems as a closed transfer window and the sense that of all the serious contenders Chelsea's squad depth is the shallowest.
None of this threatened the outward calm of the Italian, who talked of his and his team's ability to keep their nerve. "We are still on top of the League with Manchester United. We have to battle until the end of the season because Manchester United are a very competitive team," he said. "They lost against Burnley, we lost against Wigan. We have to pay attention to all the games because it can be difficult to step up. Liverpool will be a very difficult game – we are playing at home and we want to have a good reaction to this loss."
With Fernando Torres in such electric form, Ancelotti will probably not have to labour the need for Terry and Carvalho to snap a little more sharply to attention. More than anything, though, he will be looking for confirmation that what happened here was more a fleeting lapse than some first disturbing evidence of the kind of mental fatigue that accumulates at an alarming pace.
One reassurance would be a statement from Frank Lampard that he will never again look quite so anonymous in a team performance crying out for evidence of a superior will.
In the meantime, we can only acknowledge a fine day for Wigan Athletic, one that might even prove a rallying point for those who have so long been cast in the role of cannon fodder. However, another view is a little harder to resist. It is that Chelsea proved there is one thing worse than not believing in yourselves. It is swallowing far too much.
Wigan Athletic (4-3-3): Kirkland; Melchiot, Bramble, Boyce, Figueroa; Thomas, Scharner, Diame; Rodallega, Scotland (King, 88), N'Zogbia. Substitutes not used : Pollitt (gk), Amaya, Cho, Koumas, Gomez, De Ridder.
Chelsea (4-4-2) Cech; Bosingwa (Kalou, 68), Terry, Carvalho, Cole; Essien, Mikel (Belletti, h-t), Lampard, Malouda (Hilario, 52); Drogba, Anelka. Substitutes not used: Ivanovic, Zhirkov, Ferreira, Borini.
Referee: P Dowd (Staffordshire).
Booked: Wigan Thomas; Chelsea Carvalho, Essien.
Sent off: Cech (51).
Man of the match: Rodallega.
Defeat leads Ancelotti and Terry to rage in native tongues
Chelsea manager Carlo Ancelotti and his team captain John Terry spoke different languages in the wake of the team's shocking nose-dive at Wigan. But very little translation was needed.
Ancelotti, who said that when he is most disappointed in the displays of his players he still bursts into his native Italian, and Terry led a fierce dressing room inquest into an unacceptable level of effort in the 3-1 defeat.
When Terry emerged he admitted, "The manager has stressed his disappointment and the players feel that about their performance. When you come to places like this, you've got to match them – match their work-rate, win your headers, win your tackles – and we simply didn't do that in the first half. They dominated the first half and I think it was down to that.
"You can go anywhere in the world and not play well but the least we expect from every player is that they work hard and fight. We didn't do that today. That's the most disappointing thing of all. All the other big sides around us had emphatic wins today – and we come here and throw away three points."
Terry's hope is that the reaction will be ferocious in this week's Champions League game against Apoel Nicosia and in their first test of the season against a fellow member of the Premier League elite, Liverpool, at Stamford Bridge at the weekend.
"It's a massive game at home again next week and it's important that we bounce back on Wednesday night."
Ancelotti's anger at his team's collapse was under control when he returned to English. He said, "We've done very well until now and we have to make sure we respond well to one defeat."Reuse content