Nobody can predict what will happen on the field. Last season Liverpool came into the UEL as favourites, they managed to win every game before Atalanta stopped them. This season there will be a new champion in UEL, Lazio is the most consistent team so far, but that doesn't mean they can win the trophy at the end of the competition.
I don't think Man United are capable of competing in the title race, just look at their performance in the EPL, they always get minor results even though the opponents they face are not too strong.
For competitions that do have a finals to play at the end which isn't like the league settings where you actually get to win by cumulative of your points, it becomes even more difficult to really handle them because the games comes with so much uncertainties such that you may get to the finals and still not win but then it still doesn't mean you shouldn't strive to get there at least increase you chances at the luck you are hoping to get because in a way i do see it that luck has got its role to play in all of this at a time so i don't see it as primary so after the January transfer window, Manchester united may get even better and have an equal chance too.