Cape Town - English Premiership leaders Manchester City's dramatic 1-0 FA Cup defeat to third tier side Wigan was marred by ugly scenes after Sergio Aguero punched a fan.
A post-match pitch invasion by Wigan supporters at the DW Stadium saw a number of them confront City players, with Aguero required to defend himself.
TV images caught the incident as the Argentinian swung an arm at the home fan who appeared to confront the player after the final whistle.
In an uncanny repeat of the 2013 FA Cup final, in which City had a player sent off before losing to a late Wigan winner, Guardiola's side had Fabian Delph dismissed amid stormy scenes before Will Grigg's 79th-minute goal decided the game.
Earlier the drama had been provided by Northern Ireland international Grigg who capitalised on an error by Kyle Walker - who allowed a pass to run through to the Wigan man - and kept ahead of John Stones before finishing clinically from just inside the area.
It was only City's second defeat to English opposition since losing an FA Cup semi-final to Arsenal last April while their opponents can now look forward to a quarter-final home tie with Southampton.
The pivotal sending-off arrived in first half injury-time when Fabian Delph made a rash challenge on Wigan's Max Power, prompting referee Anthony Taylor to pull a yellow card out of his pocket before changing his mind and producing red.
That infuriated City players, who surrounded the referee, and the dispute spilled into the rival technical areas with Sergio Aguero having to be dragged away by Guardiola as he argued furiously with Wigan coaches.
The scene turned even uglier, with television cameras in the tunnel capturing footage of Guardiola and Wigan manager Paul Cook in a major verbal confrontation and being kept apart by staff.