He failed to punch away a corner, allowing Frazier Campbell to nip in and put the Welsh side into a lead they never let go of.
That, together with a mistake that allowed Scotland to go ahead against England at Wembley earlier in the month, has raised a few questions over the form of the 26-year-old.
Hart has been City's No. 1 since Roberto Mancini opted for him over Shay Given at the start of the 2010-11 season, but could Manuel Pellegrini look elsewhere? Or does he stick with the Shrewsbury-born stopper? Here are a few options the City boss may be mulling over.