Pep Guardiola saw off Jose Mourinho in this town without breaking sweat, only to find a more dangerous foe rising 35 miles away in Liverpool. But the threat posed by Jurgen Klopp is bringing out the warrior in the defending champions' manager.
When the pre-match mutual admiration ceased, two teams with 136 league and cup goals between them tested the theory that City's title defence was being broken as early as January by the Liverpool renaissance.
And the two generals stood in their coaching zones trying to appear in control of a rivalry that now burns in vibrant colours.
If these are the new superstar managers in England - and this the new power struggle at the top - the good news is that both clubs have the players and the character to justify the hoopla.
The new year started not with a whimper but a bang: a game that might have sent Liverpool 10 points clear and their opponents into introspection.
City's revels ended with three defeats in four. December turned them from hunted to hunters.
Guardiola said nobody "trusted" City any more - by which he presumably meant "believed" in them. But his players evidently still believe in themselves.
One of Guardiola's tricks has been to change Sergio Aguero from pure predator to mobile forward and contributor to the patterns woven around him. But one of Aguero's attributes required no modification: his finishing.
With City's lucky goal-line escape behind them - and Vincent Kompany fortunate to be still on the pitch after his airborne tackle on Mohamed Salah - Aguero smashed the ball past Alisson from an acute angle and with a force no goalkeeper could hope to cope with.
In these games, you see the real pros step up. Guardiola, who flew into a rage six minutes from time, has no need to tell Fernandinho or Aguero what to do; and Klopp can expect Virgil van Dijk and Salah to know the drill.
Aguero's goal celebration affirmed his place in City folklore. He knows how this all works, and what City needed to fight their way back into this title race. They needed everything - and everybody.
Guardiola's men, though, have been forced off their smooth path to world domination. They have had to adapt to Liverpool.
At Anfield, Guardiola cleverly negated Liverpool's forward three by spreading the game wide and passing bravely from the back to deny Klopp's side possession.
Here, with the title supposedly on the line three days into 2019, City went "longer" than usual, striking direct passes behind the Liverpool full-backs.
Some of Fernandinho's passing was sublime, and Raheem Sterling owes him a drink for at least two fizzing deliveries from deep positions.
So Guardiola is far more flexible than his image suggests. He would probably rather carry on passing teams to death but Liverpool have forced him to adjust his personnel and his approach.
No chances were taken with a back-four that featured four centre-backs (Aymeric Laporte played left-back) and City were combative from the off.
For them it was no beauty contest but a retrieval mission, to put them back in the race.
The Premier League has whipped up many dugout duels, from Alex Ferguson versus Kenny Dalglish and Kevin Keegan to his long struggle with Arsene Wenger, which passed from animosity to friendship.
Ferguson's battle with Jose Mourinho was undeclared. Neither wanted to provoke the other.
Guardiola v Klopp, though, is a struggle between purists, but not dreamers.
The hard edge brought to management by both these creative thinkers adds an element that would not be there if each was simply an artist with a pretty vision.
Both come to fight, to win. Each tries to mobilise emotion in the service of power. Both live on the edge in pursuit of conquest. In that quest to pinch an inch, psychologically, Guardiola and Klopp both praised each other's teams this week in a mixture of respect and passive aggression.
Early in 2016, Guardiola described Klopp as the best attacking coach in world football.
Both teams have character, hunger, for which we ought to thank the managers
After you, Claude? Not for a second. Klopp, with two Bundesliga titles to Guardiola's three league crowns in Spain, three Bundesliga titles and two Champions League triumphs, is looking to usurp his younger rival as English football's No 1 coach.
He rides a storyline better than City defending their title. To return the championship to Anfield 29 years after it departed would put him in the pantheon with Bill Shankly, and on 63 minutes he took another small step in that direction when Roberto Firmino equalised at the end of some good work by Liverpool's full-backs.
That goal told you everything about Liverpool's maturity, their self-belief.
But City are not novices at this. Leroy Sane, who performed with great purpose throughout, broke on to a Raheem Sterling pass and drove the ball in off Alisson's left-hand post.