WIGAN, England -- Pep Guardiola always maintained it was unrealistic to think that Manchester City could win the quadruple, but it's almost more unfeasible that a side battling for promotion from League One would be the ones to kill off that dream.
City have gone to Premier League champions Chelsea, bitter rivals Manchester United and Serie A leaders Napoli, dominated them on their own ground and won. Meanwhile, title rivals Liverpool, Tottenham Hotspur and Arsenal were methodically taken apart at the Etihad Stadium.
Before Monday night, Man City had lost just twice all season. The first was the final inconsequential game of their Champions League group away to Shakhtar Donetsk and the other a pulsating Premier League defeat to Liverpool.
Yet despite that, it is Wigan -- with an average attendance of fewer than 9,000 this season -- that ended City's hopes of writing their names in the history books with an unprecedented clean sweep of four trophies by knocking them out of the FA Cup.
While the Latics are not quite the ragtag assortment of plumbers and bus drivers normally associated with the greatest cup shocks, they are hardly a team of celebrity names either. Chey Dunkley, who was playing for non-league Kidderminster Harriers three years ago, was unbeatable in the centre of defence next to Dan Burn, signed on a free transfer from Fulham.
Goal hero Will Grigg is well-known for his personalised chant "Will Grigg's On Fire" but the Northern Ireland international has only scored once for his country and has only played one season in the Championship. Midfielder Nick Powell has been predicted to make a step back into the top flight but managed just three starts at Manchester United in four years.
Yet somehow Wigan managed to shock a side under Guardiola that many thought was rewriting the rulebook on how to play football in England.
Statistically it seemed like a straightforward, dominant performance from City. They had 83 percent possession and 29 shots -- although just five were on target and ex-Brighton reserve keeper Christian Walton pulled off a couple of excellent saves.
"They scored from one shot on target from our one mistake," Guardiola said after the game. "We created good chances but in these kind of games, sometimes you cannot score a goal."
The City boss was keen not to blame Fabian Delph's sending off for the defeat. The England international was given a straight red card for his lunge on Wigan's Max Power -- although referee Anthony Taylor had initially taken out a yellow card.
It appeared that Guardiola wasn't too happy with the decision at the time, as both clubs' benches were embroiled in an argument that spilled into the tunnel as the players left the pitch at half-time.
"It's a red card. It's an unnecessary action," Guardiola said. "The referee decides what he decides. It can be a red card."
Although opinions were split amongst pundits about whether it was worth a sending off, it was the sort of lunge that Guardiola has been imploring referees to take action against. But it wouldn't be surprising if the Catalan was frustrated that his player was punished when he has seen so many opponents escape with yellow cards.
Guardiola must now cope without Delph for three domestic games, including Sunday's Carabao Cup final against Arsenal. Monday night's defeat will give Arsene Wenger's side added hope that they can cause another upset at Wembley.
City will still go into the game as big favourites but Guardiola will be desperate to prove that there is no self-doubt left over from the defeat to Wigan.
A number of his players were below their best at the DW Stadium. Kyle Walker has been faultless all season but made an uncharacteristic error that led to Grigg's goal, John Stones was hesitant and unsure while club-record signing Aymeric Laporte is still getting to grips with English football.
Arsenal caused a surprise at Wembley last season when they beat City in the FA Cup semifinal to ensure that Guardiola finished the season without a trophy for the first time in his managerial career.
Since that game last April, City appear to have got significantly stronger and the Gunners considerably weaker, but Wenger will still believe that he can make the Spaniard wait a little longer for that first silverware.
Guardiola will at least have Raheem Sterling and Nicolas Otamendi back after they were rested for the trip to Wigan, while Kevin De Bruyne will start after only coming on as a substitute Monday.
Should Arsenal pull off another -- though slightly less surprising -- upset, then doubts might start to creep in going into the final months of the season, although it's difficult to see City blowing up in the title race with a 16-point lead.
A place in the quarterfinals of the Champions League is all but secure after a 4-0 first leg away win to Basel, but the biggest tests are still to come and City can't afford to lose their belief now if they are to challenge for their first-ever success in the UEFA competition.
But frustratingly City have fallen just two games short of Guardiola being forced to consider the quadruple a slight possibility.
"Ask the question in March or April if we are still in all four competitions," Guardiola said at the turn of the year.
It was always a long shot, but no one could have expected the impossible dream to end at the DW Stadium.