He has started to become selfish again as far as I can see. This isn't good at all. Manchester United need a solid team effort these days to start recovering again. Their target must be no less than finishing in top four. This needs a solid and consistent performance.
I don't think you should write Manchester United off that top 4 despite the fact they're having problems they can't identify, this guys have their way of doing things with that last minute of the season and this distraction of the champions league is another issue that they can't add up with the frustrated form they have in the EPL.
The coach on the other hand is running out of options like he doesn't know the style to play any more. Is best he starts thinking of a new strategy because the old one isn't helping at all and I don't think changing the coach is going to be a good idea, it will make things worse and that's when they won't make it to the top 4.
You won't blame him, I believe he wants to do like his mates talking about the likes of Bellingham or Mbappe and some other players of his age, he (Rashford) just thinks he had to carry the burden of the club on his shoulder, that will only bring a one man soldier on the field which will increase his selfish behavior.
So is best he always start from the bench and not to stay off the field of play, it will kill his momentum because as it is, Rashford is like the face of UTD.
Take a look at the Man UTD team, do they look like a team that have quality players to replace anybody from the starting 11? They're just trying to groom some of the teenages to the first team. For example Alejandro Garnacho Ferreyra has joined the senior team and played out his best and ever since ETH stopped starting him from the bench he has never been that great player United saw in him. And I can't say emotions has ever been attached to ETH's decision on who to play or not.