The England international is under yet more scrutiny after a mix-up between himself and defender Matija Nastasic led to Chelsea's late winner in Sunday's Barclays Premier League clash at Stamford Bridge.
It was the latest of a series of errors to have blighted the 26-year-old's performances for club and country over the past year.
It would not be unusual in itself if Hart were to be replaced by Costel Pantilimon for the fourth-round tie at St James' Park, as the Romanian has often been preferred for cup fixtures in the past two seasons.
But given the increased speculation over Hart's position - after previous mistakes against Scotland, Cardiff, Aston Villa and Bayern Munich this season - the match could give him the opportunity to stake a claim for a regular place.
Pantilimon, also 26, has not played in the Premier League since joining City from Timisoara in the summer of 2011 as replacement for Shay Given.
Manager Manuel Pellegrini declined to answer questions specifically relating to Hart after the Chelsea loss and has previously said he is not immune to the axe.
That suggests a good performance against the Magpies could earn Pantilimon the chance to start the Premier League game against Norwich at the Etihad Stadium at the weekend, although that remains to be seen.
City's task at Newcastle will be to start rebuilding momentum after the last-gasp loss on Sunday.
For all their brilliance at times this season - including their 4-0 thrashing of Newcastle when they met in August - their form has been inconsistent.
Defender Pablo Zabaleta sees the cup as a good opportunity to get back the winning feeling.
The Argentina international also believes last season's shock loss to Wigan in the FA Cup final has provided extra motivation to impress in the domestic cups this time.
He told the club's website, www.mcfc.co.uk: "Last season hurt us. We finished second to (Manchester) United and lost the FA Cup final and this club cannot accept silver medals.
"The manager always tells us that we have the squad to challenge in everything and that he will always try to put a strong team to win every game.
"The experience against Wigan has made us more focused. This time the manager has told us that we must aim to win all four competitions that we are in.
"I think that's what you want to be aiming for when you want to be the best team."
Pellegrini is expected to make further changes for what will be the club's fourth away game in the space of 12 days.
Striker Stevan Jovetic, who scored twice against Wigan in round three but has not started since, is likely to get another opportunity.
English trio Micah Richards, Joleon Lescott and James Milner are also prime candidates to play.
Exciting Portuguese youngster Marcos Lopes, who shone against Wigan, will not feature after tweeting that he had suffered an injury on the eve of the game.
He tweeted: "Injured :-/ Nothing too serious but as all injuries: #badtiming. Be back soon.."
Captain Vincent Kompany, who has missed the last three games with a groin injury, remains a fitness doubt but midfielder Jack Rodwell could be in contention after his latest hamstring problem.
August deadline day signing Martin Demichelis - the defender who made a belated debut at Chelsea after overcoming a knee injury - could be given another run-out.
Zabaleta, who was the club's player of the season in 2012-13, has been impressed by all the summer arrivals.
He said: "The new signings have all brought something different.
"Alvaro Negredo, Jesus Navas and Fernandinho have settled in very quickly and have already had a big impact.
"Jovetic and Demichelis haven't played a lot of games yet but they will get their chance.
"I think they have made the team much stronger."