Even without participating to any European football, and that means the team can rest way more than the others, I really don't see how Manchester United could somehow be a contender for the Premier League. The team they have makes little sense, they have no real striker at the moment, just a bunch of random players. The goalkeeper is a disaster. Maybe, and it's a big maybe, they can reach a Champions League spot.
MU will never be a premier league contender until they can sell all of their players, then rebuild the squad from the scratch by focusing on the collectivity gameplay like what PSG did. They have so many useless players in the squad, and must get rid 80% - 90% of them.
Even a transfer news account already spilled this to them.