1. He should stick to his guns overall. In principle what he's trying to do makes sense, and he's bought the right profile of players for it, and they all not only have the right pedigree but have very recently all been in good form, either for us or elsewhere. Form is temporary, class is permanent and all that.
2. Externally, he must highlight that we are riding out a serious injury crisis. With some luck, by the end of October, the starting XI will be looking significantly better, because a number of our FB options will be available again (including Shaw, hugely valuable to the team in his own right). That will allow us to either replace or combine Casemiro with Amrabat, which should ease our biggest consistent issue since the start of the season, our defensive weakness through the middle.
Internally, he must talk as little as possible about the injury situation, and instead hold the players to a higher standard, especially the experienced ones. I expect he already is: these things aren't always like waving a magic wand.
3. He must stick by Onana. It was never going to be easy to adapt from one of the most line-hugging to one of the most ball-playing top-level GKs in the world. We all knew this, and plenty said it. We are in the same adjustment period in which De Gea was getting battered for failing to claim crosses. It takes time. Onana will settle, and the rest of the team will adjust to how to play with him.
4. He should move Rashford to the right and start Garnacho on the left. Hojlund looks capable of being a consistent goal threat, and regardless of who's new and who's the 'star' player, you should build an attacking unit that allows your CF to score goals. That's conventional wisdom for a reason.
Of course for fans it's maddening to see the season slipping away after all the promise of last year. Fans are reactive. Sadly so are owners. But even given the latter, I think as a manager you have to ask whether your approach is a logical one given the resources available, and if it is you have to stick at it.