The champions of England breathed new life into their title defence on Thursday night, but they now face an entirely different test as they look to avoid an upset against the Championship strugglers.
It is not often that Manchester City have gone into a game as underdogs over the past 16 months or so, but there were plenty of people backing Liverpool to get something from Thursday's top-of-the-table showdown.
The Reds had won nine league games in a row heading into the match, whereas City had lost three of their last five and were in danger of slipping 10 points behind - and perhaps out of the title race altogether.
However, it was the champions who emerged victorious from a frantic contest amid a rousing atmosphere inside the Etihad, closing the gap back to four points and leaving them with Jurgen Klopp's league leaders firmly in their sights once again.
The ambience is likely to be a lot more relaxed and subdued three days after that rip-roaring encounter, and there will be no doubt about City's status as overwhelming favourites when Rotherham come to town.
The Premier League and the Champions League remain higher up the priority list, but Pep Guardiola's side aim for success in every competition they enter, and their recent dip in form should not fool anyone into thinking that they are not capable of it.
FA Cup glory is the only major domestic honour which has eluded Guardiola in the English game after he picked up the league and EFL Cup last season, while City have not won it since their 2011 triumph which ended a 35-year wait for notable silverware.
Indeed, it is a big week for Man City's trophy hopes having already kept themselves alive in the Premier League title race, with this FA Cup tie being followed by the first leg of their EFL Cup semi-final against surprise package Burton Albion.
Consecutive games against lower-league opposition may not feel as much like a final as Thursday's match against Liverpool, but it is knockout football and any slip-up from Guardiola's side could prove costly to their quadruple dreams.
Such a scenario on Sunday may look unlikely considering the talent at Man City's disposal, but remarkably they have won just three of their last seven FA Cup games against sides from a lower division, losing three of those too.
That run includes a fifth-round exit at the hands of Wigan Athletic last season - a team that, at the time, were ranked below Rotherham in the Football League pyramid.
There is hope for the visitors, then, but it is worth noting that this will only be Guardiola's third home FA Cup game in charge of City, and he has won the previous two by an aggregate score of 9-2.
Recent form (all competitions): WWLLWW
It is less than eight months since Rotherham last graced the Wembley turf as they secured an immediate return to the Championship via the playoffs, but the road back to the national stadium could not get off to a harder start than Man City away.
The Millers may take heart from the fact that Man City have suffered a few giant-killings in this competition in recent years, although even manager Paul Warne admits that it will take a bit of cup "magic" for his side to prevail.
History certainly does not seem to be on the visitors' side, with Rotherham failing to win a single FA Cup game since a 3-0 triumph over Bradford City in November 2013.
Five subsequent FA Cup games have resulted in five successive FA Cup defeats, conceding two or more goals in each of those games and 14 in total.
Not since the 2001-02 campaign have the Millers made it further than the third round, while they have only ever made it to the fifth round on two previous occasions, so hopes will not be high amongst the fans of a lengthy cup run this season even if they are to topple the champions of England.
Rotherham did make it to the second round of the EFL Cup earlier this season before being beaten by Everton, but since August they have only had the Championship to focus on.
Warne will consider Sunday's match of secondary importance to the ongoing relegation battle which his side find themselves embroiled in, with just one place and three points separating them from the relegation zone in the second tier.
The visitors do at least come into this match off the back of a rare win, having ended a nine-game winless streak by beating Preston North End on New Year's Day.
Not since August have the Millers won back-to-back matches, but they have been draw specialists of late with 10 in their last 17 outings, and they would certainly take a return fixture at New York Stadium if they are able to hold off their illustrious hosts.
Such a result would take a monumental upset - and perhaps a sprinkling of the magic Warne is after - but stranger things have happened in the FA Cup.
Recent form (all competitions): DDLLLW
City could welcome Kevin De Bruyne back into their starting lineup for this one as he looks to get minutes under his belt following his latest injury absence.
The hosts are expected to make wholesale changes from the win over Liverpool, with the intensity of that game meaning that Guardiola could bring in 11 new players for this match.
Youngsters Phil Foden, Eric Garcia and Brahim Diaz are all in contention to feature, while even in a second-string side the likes of Kyle Walker, Nicolas Otamendi, Ilkay Gundogan, Riyad Mahrez and Gabriel Jesus are in line to start.
Rotherham, meanwhile, will have to cope without midfielder Ryan Manning, who has had his season-long loan move cut short by parent club Queens Park Rangers.
Man City possible starting lineup:
Muric; Walker, Garcia, Otamendi, Zinchenko; De Bruyne, Gundogan, Foden; Mahrez, Jesus, Diaz
Rotherham possible starting lineup:
Rodak; Ajayi, Robertson, Wood, Mattock; Taylor, Vaulks, Palmer, Williams; Wiles; Smith
Head To Head
Man City have never lost in 10 previous meetings with Rotherham, winning seven of those including the only previous FA Cup tie.
On that occasion the two sides played out a goalless draw in the third round of the 1978-79 campaign, before City won the replay 4-2.
These two sides have not met in any competition since a second-tier clash in March 2002, when a Rotherham team including current boss Warne held a Man City team including Shaun Wright-Phillips, Shaun Goater and Stuart Pearce.
We say: Man City 4-0 Rotherham
The only danger for Man City in this match seems to be some sort of hangover from Thursday, but considering the likelihood of 11 changes that should not be a problem. It should be a comfortable afternoon for Guardiola's side.