What's top 4 sides got to do with it? And if you do want to look at that, let's look at what's left, not what's gone. Liverpool have to play 2 more away games against top 4 clubs. Man Utd have 4.
Let's assume you want to get 4th place. That's normally going to be about 70 points. You have 13. So you probably need another 57 points on the table. That's 19 wins from 27 games. You can't beat Chelsea at home, so no chance are you winning at their place. You also still have to play City twice. Let's be optimistic and say you can get 3 points from those three games. I don't see how, but let's try it and see what happens.
You still need 18 wins, but now you only have 24 games. But you still need to visit Anfield. And the Emirates. And Goodison. And White Hart Lane. Think you can win two of those four? Great. That's title-winning form. Now you just need 16 wins from 20. And you still have to play Liverpool, Arsenal, Spurs at home.
And in all of this, you need to avoid slipping up against the likes of Southampton, West Ham, Swansea, Hull, Stoke, real banana skin clubs, not to mention any more of the Leicester/Burnley/Sunderland cock-ups.
Thing is, none of it's impossible. There is still a chance on paper. But it would require this Manchester United side to go on a run that would be better than anything the club has ever done before. Personally, I don't think that is very likely at this point.