League one side, Wigan pulled off one of the biggest shocks of recent seasons as they dumped runaway Premier League leaders Man City out of the FA Cup.
Northern Ireland striker Grigg struck the decisive goal 11 minutes from time against a side often heralded as Europe’s best this season as Man City hopes of a quadruple were ended in staggering circumstances.
The first half saw Sergio Aguero twice go close, while Fernandinho blazed a great chance over the crossbar when the ball dropped to him six yards out.
Grigg also hit the side-netting for the hosts following a lengthy run as Wigan held their own against their big-money opponents.
The game’s major talking happened in first-half stoppage time when Wigan only half cleared a City corner and Fabian Delph went lunging into a 50-50 challenge that left Max Power in a heap.
Referee Anthony Taylor originally reached for yellow but produced a red after a seemingly late change of heart. The decision left Pep Guardiola incensed and several players, Delph included, confused.
City predictably attacked in waves, but there was no way through as Paul Cook’s side repeated their 2013 victory in the FA Cup final to book a place in the last eight of the 2018 edition and leave City’s Quadruple dreams in tatters.