Pep Guardiola was involved in a furious row with Wigan boss Paul Cook as Manchester City's quadruple bid was sensationally derailed by their FA Cup bogey team on Monday.
Will Grigg scored a stunning late breakaway goal as third-tier Wigan repeated their shock 2013 final victory over City in a fiery fifth-round tie at the DW Stadium, winning 1-0.
The main talking point came on the stroke of half-time as City's Fabian Delph was controversially sent off and an irate Guardiola became embroiled in a touchline argument with Cook.
The pair continued their row in the tunnel as the teams left the field at half- time and they had to be separated by colleagues.
After all Guardiola's recent complaints about bad tackles on his players, Delph was dismissed for sliding in on Max Power.
Yet, despite their numerical disadvantage, City only had themselves to blame for spurning a host of chances against the League One side.
Grigg made them pay in the 79th minute as Latics secured another famous victory over City following their 2013 success and another in the quarter-finals the following year.
Against the odds, it is now they who go forward to a last-eight tie with Southampton and not the runaway Premier League leaders.
City dominated possession throughout but could not take advantage. Sergio Aguero headed over early on and Ilkay Gundogan forced a good save from Christian Walton.
Gundogan found himself in another good position only to miskick and Aymeric Laporte also failed to make clean contact in front of goal.
Fernandinho blazed over from a gilt-edged opportunity about eight yards, Gundogan missed the target with another effort and Danilo dragged a shot wide.
Yet all the while, Wigan were defending stoically and threatened occasionally on the break.
Controversy erupted when referee Anthony Taylor dismissed Delph following a sliding challenge on Power.
Taylor initially had a yellow card in his hand, but eventually brandished the red one, sparking vociferous complaints from City players, who felt the decision was harsh.
But late in the match, Grigg capitalised on a Kyle Walker error to win it for Wigan and grab the headlines.
Cook said: "It was such a severe test, in everything. They are such a good side, they move the ball so well.
"Tonight we had to ride our luck at times, the sending off is always a big incident in the game.
"We had to ride our luck with a couple of flashing crosses, but that's what makes the FA Cup so special.
"Our lads deserve a lot of credit for the amount of work and the level of energy they put in. To beat a Man City team you have to do that."
There were some unsavoury scenes following the game as Wigan fans invaded the pitch, with supporters from both clubs involved in disturbances.
Television pictures also appeared to show a Wigan fan and Manchester City striker Sergio Aguero involved in a physical exchange on the pitch.