As many runners will have experienced, when you buy a new pair of trainers the temptation is to wear them all the time - and why not? They're more comfortable than your old battered pair, they look better and - whether a psychological side effect or not - they make you run that little bit faster.
But one day there will come a time when you have to crawl back to the very shoes you so eagerly disregarded. Maybe your new wheels are still soaked from the day before, or you're running a trail and don't want to dirty your road shoes. Whatever the reason, when you run there's something missing; that bounce isn't there, that extra spring in your step that comes with confidence and being comfortable. It just doesn't quite work.
On Tuesday evening in Copenhagen, Manchester City experienced something similar for the first time in years. Pep Guardiola 's side played out a goalless draw against FC Copenhagen in their fourth Champions League outing of the season, six days on from thumping the same opposition 5-0 at home.
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On the face of it, a 0-0 draw was a good result. City didn't play particularly well in a game that became dominated by VAR controversy - Rodri had a spectacular effort incorrectly chalked off for a handball in the build-up, Riyad Mahrez missed a penalty rather harshly awarded for another handball and Sergio Gomez was (correctly) sent off after 30 minutes for a mindless last-man foul.
In the end City were happy to get away with a point, and thanks to Borussia Dortmund's 1-1 draw with Sevilla later in the evening, it proved enough to secure City's place in the last-16. Job done.
However, upon closer inspection, City's rather blunt attacking display was directly linked to the elephant in the room - or rather not in the room. Erling Haaland spent the evening on the bench, Guardiola explaining that he was "so, so tired", after the Southampton win on Saturday.
Haaland has been nothing short of a sensation since he arrived at the Etihad Stadium. The 22-year-old striker has scored 20 goals in his first 13 games for the club - including three hat-tricks - and has already smashed a ton of records. The problem now is how do City make sure they perform when their new trainers can't be worn?
It's a question of adaptation and versatility. Under Guardiola, City have won four Premier League titles and reached one Champions League final without the help of Haaland. Clearly, they can be wildly successful without him.
The issue now is that they have become used to playing with him. During pre-season Guardiola assured reporters and fans alike that his side would not change its style for one player, and that Haaland would have to develop aspects of his game in order to fit in. That is largely true, but there is no denying that Haaland has given City something they lacked before, something they have so far this season come to rely upon.
In Haaland's absence Julian Alvarez started up-front in Copenhagen, but City's attacking approach was the same as it always is. Short, intricate passing, overloads on the flanks, pulling the defence this way and that in order to create gaps.
The problem was that Copenhagen's defence was extremely organised and compact, and they left very little space between their defensive and midfield lines in which City could play. That's nothing new, but it was in those kinds of games last season that City sometimes struggled.
This year, Haaland has gone a long way to solving those issues. Whether he's taking advantage of a high defensive line - Copenhagen's was reasonably high - by running in behind, using his instincts to be in the right place at the right time inside the penalty area or simply distracting defenders with his presence to create space for others to attack, Haaland gives City many more options for breaking down opponents.
When Haaland is not in the team - and that will happen again this season - City need to revert to how they used to do things, or risk pinning all their hopes on one individual.
After the match Guardiola confirmed that Haaland is not injured, he was just very tired. On Sunday City will be able to enjoy that new trainer bounce again - hopefully the next time they don't wear them their performance doesn't dip too much.
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