Guardiola had made six changes for the tie, while still fielding a strong line-up, but two of his fringe players — full-back Danilo and back-up goalkeeper Claudio Bravo — were guilty of errors which offered the hosts a glimmer of hope.
First Bravo and Danilo dithered in dealing with the ball, almost presenting Gareth Roberts with a chance on the six-yard line.
And then Danilo was robbed of the ball by Roberts, the ball breaking for Grigg who raced half the length of the field before shooting into the side-netting.
? ? @mp_1825 #wafc pic.twitter.com/Re1NFd4Vi6
— Wigan Athletic (@LaticsOfficial) February 19, 2018
City were enjoying the bulk of possession but, without the rested Kevin De Bruyne and Raheem Sterling, were struggling to create clear chances.
They came close, from Leroy Sane’s 26th-minute corner which Gundogan flicked across the six-yard area, but defender Aymeric Laporte failed to connect with the ball at his feet.
When City next threatened, after Stones headed down Delph’s cross, Fernandinho’s shot rose over by some distance when he looked certain to score.
Gundogan and Danilo, twice, also threatened the Wigan goal and Walton saved superbly from an Aguero drive, moments before the explosive dismissal of Delph.
Guardiola brought on England right-back Walker as a half-time substitute, moving Danilo over to Delph’s vacant left-back spot.
? Only one stat that matters tonight ?#wafc ?⚪ pic.twitter.com/NJ6CCIMvwD
— Wigan Athletic (@LaticsOfficial) February 19, 2018
Despite their disadvantage, City still enjoyed the majority of possession although, apart from Chey Dunkley blocking a Danilo shot, there was little to concern Walton as the tie approached the 65-minute mark and Guardiola opted to bring De Bruyne into the fray.
The Belgian’s introduction brought a far greater threat from City, particularly from set-pieces.
On 73 minutes, De Bruyne found Aguero at the near-post but his shot was blocked and Danilo maintained the pressure with a low centre across the goalline before Grigg’s dramatic intervention.