It is remarkable how a lead at the top of the English Premier League table can seem comfortable one minute but dwindle to just two points with one passing result.
While it is still a bit premature to label the contest a title-decider, it may prove to be a turning point in Manchester City's quest for its first title in England's top flight since 1968.
It's not how you start, but how you finish, the old adage goes.
Manchester City has been supremely impressive to this point in the season, but so have several other teams over the past only to crumble down the stretch and see their grip on silverware slip away.
True championship form is most often exemplified by how a team performs in crunch time, when the pressure is really on over the last few months of the season.
No team displays those kinds of title-winning performances in the final months more than City's main title threat, local rivals Manchester United.
The Red Devils are as notorious for slow starts in the opening months as they are for turning on the back-burners late in the season, a run-in often referred to by United manager Sir Alex Ferguson as "squeaky bum time."
Manchester United has won four of the last five English Premier League titles with minimal player turnover, allowing for chemistry to develop and continuity to breed success.
The likes of Wayne Rooney, Ryan Giggs, Rio Ferdinand, Michael Carrick, and Patrice Evra not only have experience in a title chase, but they have more often than not come out on top in those instances. They know what to expect, and they know how to come back after a loss like the one Manchester City suffered Monday.
Manchester City, meanwhile, does not have that same sort of experience. Granted, it has a plethora of players who have competed at the highest level, but it has very few players who are familiar with a winning tradition.
How will the Citizens be able to cope with a depleted squad should Roberto Mancini's men become ravaged by injuries? How will the rest of the team respond should Mario Balotelli's constant antics off the field become too much of a distraction? And will they allow inevitable losses to fester and lead to more dropped points?
These are all questions that raise suspicion as to whether or not Manchester City can be declared the title-favorite yet, but the most compelling suggestion that Monday's loss could be a turning point in the championship race derives from the fact that the Citizens are no longer unbeatable.
To this point in the season, Manchester City held the psychological edge over its opponents before even stepping onto the field. That's what a 6-1 win over Manchester United and 12 wins from its first 14 games will do for a team.
But now the rest of the Premier League has taken notice, and they've seen that air of invincibility disappear.
Teams will line up alongside Manchester City every week looking to have a go, knowing that they realistically stand a chance to come away with three points against the most valuable squad in the Premier League.
Of course, it is also possible that City responds in championship fashion, rattling off another long string of convincing victories to affirm its status as global soccer powerhouse. But it may just spark a dip in form that would tip the scale back in favor of second-place Manchester United.
Come May, when one team hoists the Premiership trophy at season's end, we could be looking back at a Monday in December as what proved to be the tipping point in the race for the title.