One of the most eye-catching aspects of Manchester City's approach at Anfield in October was Pep Guardiola's insistence that his full-backs hold their position and limit the room in which Liverpool's flying forwards could attack in behind.
He had vowed not to change his way of playing in the build-up to that game but, wary of the way Liverpool mercilessly exploited the space in behind his full-backs in their previous three meetings, here were Kyle Walker and Benjamin Mendy under instruction to play conservatively and focus not on bombing forward but stifling Mohamed Salah and Sadio Mané.
It became pretty obvious very early on that Guardiola was going to adopt a similar tactic at the Etihad Stadium last night, albeit with different personnel which highlighted some of the unforeseen problems with which the City manager has been wrestling this term, the sort of which, on top of poorly-timed injuries to key midfielders, would have derailed most teams.
The success with which Danilo and Aymeric Laporte tackled their rather forbidding assignments was always likely to have a telling impact on the outcome of this game and, by extension, largely define Guardiola's gameplan. Shackle Salah and Mane and you suffocate Liverpool, or so the thinking goes.
Still, it is a curious sight to see the full-backs in a Guardiola side this reluctant to venture beyond the halfway line. The tactics were simple: sit tight, do nothing rash, don't get sucked upfield.
Laporte's presence high up the field in the 40th minute, delivering a cross that Liverpool failed to clear properly and from which City eventually scored, actually felt like an outlier so deep did he play.
He was certainly a lot more disciplined than he had been as a makeshift left-back in the 3-0 defeat to Liverpool in the first leg of their Champions League quarter-final meeting at Anfield in April, although he was as much a victim of City's narrow, congested midfield and Leroy Sané's failure to track back that night as any personal shortcomings.
If it was a significant call to play Laporte there again, even if the options were limited with Mendy still out injured, Fabian Delph suspended and Oleksandr Zinchenko simply not trusted, but arguably the biggest gamble came on the opposite side.
The idea of Danilo being preferred to Walker in a game of this magnitude a few months back would have been unthinkable but it underlined the extent of the England defender's plummeting form that the Brazilian was favoured for the third game in a row. Walker has been struggling for some time, and the 3-2 defeat at home to Crystal Palace, when he clumsily conceded a penalty, proved the final straw.
City's investment in almost £130m worth of new full-backs in Guardiola's second summer was a potent symbol of City's brave new world under the Catalan. Yet here they were, in the biggest game of their season, having to improvise in positions they thought they had addressed but which require further surgery.
This was a true test of Guardiola's acumen. Could he curb Liverpool's rampant front line with a back line he seldom envisaged?
What Guardiola certainly did not want was Andrew Robertson and Trent Alexander-Arnold doubling up on the flanks with Mané and Salah, which was why it was imperative that Sané and Raheem Sterling did everything they could to occupy Liverpool's full-backs.
How galling it must have been for Guardiola, then, to see Alexander-Arnold and Robertson, hitherto pegged back, combining to set up Liverpool's equaliser for Roberto Firmino.
But City's reaction was swift and it was somehow fitting for Sterling and Sané to dovetail for that second goal. Sterling's pass was deft, Sané's finish precise, just rewards for an evening of enterprise and endeavour.
City have been patched up for weeks now but emerged triumphant in their fiercest test yet. It will imbue Guardiola with huge confidence over the second half of this campaign. (© Daily Telegraph, London)