This. Football is not played half-assed at this level. I cannot understand people are really suggesting we should not play "properly" and let the opponent win, to save some of our energy to the next match. I don't think it works like that.
The schedule was tough in this one (City, then Milan), but I'm not sure if City match affected the players in a way that if they played City match with energy-saving mode, we would have won Milan. Like how the coach could even suggest such thing to the players? We already used few reserves in that match (Taremi, Zielinski, Bisseck), but is the suggestion we should have used Asllani, Augusto, Arnautovic, De Vrij also?
Anyway, saying "winning the league this year is an absolute must" is quite a statement, given the added games we have and specially versus the competition we have now in the league. All our rivals are better and in my books our main rival for the title (Napoli) has just Serie A to focus on. That's around 9-10 less games by January (then CL knockout games on top, let's say 2-4). So probably at least 9-11 more games (Super Coppa included), in 5.5 months.
I wrote about this before the City game (had an aged-like-milk Milan joke as well which I won't refer back to, lol), but the Man City game was, mathematically speaking, the least important game we'd play in the league phase, quite possibly least important game we'll play all season. It was in Manchester, so unlikely to win, and it was the first game of the league phase, so plenty of time to make up ground for an early setback. Anything we got from that game would be a bonus, nothing much was expected.
But that's the FM way of looking at it. It doesn't work like that in real life. In real life, that was a CL Final rematch from just 15 months prior. Many players in our lineup that night are still here. Nothing we did that night would make up for the loss in 2023, but there would nonetheless be an air of unfinished business, being happy to get another crack at them just to see how we level up. That playing them as well as we did that night, even in defeat, wasn't just a fluke. (This is where I'll also remind that it was spoken about how our performance that night, and the confidence taken from seeing that we could play up to that level and push a treble-winning Man City side to the limit, helped fuel our excellent 2023-'24 season.) Man City is a team we quite possibly will need to get past later on this season if we harbor any Champions League ambitions - forget Oaktree; the players and coaches are going to have this kind of goal whether it's "realistic" or not - so what better way to get an early read and some video on them than playing them directly.
The fact is, that Man City game was always going to be taken more seriously than its placement on the calendar dictated because that's how human nature works. There was no scenario to speak of where "oh, we've got the derby on Sunday, we need to prioritize that, rotate if needed in England, etc." was ever going to happen. Imagine facing arguably the best team in Europe and then telling Lautaro "we're sitting you" and imagine how that goes over. It doesn't, that's how you upset players and dressing rooms in general. We're not some tiny club, we're a fucking defending league champion, nobody is going to back down from a challenge.
The calendar did us no favors. Milan had a difficult CL opponent as well, but they had an extra day of rest and they played at home. Whatever. (It also doesn't help us this week either; we play on Wednesday in Switzerland - admittedly not a long flight from Milan - while Juve play at home today.) That's on us to figure out a way to deal with it. Strong-mined teams brush aside those problems, weak-minded teams use them as an excuse after they lose.