I think I disagree with you on the point that Arsenal will be the winner of the tournament. Personally, I think that Barcelona is a better team than both them and United.
Manchester United have not been playing very well football this season, and on top of that, they had that Cristiano Ronaldo controversy as he was released from the team.
Compared to that, Barcelona have Robert Lewandowski, who will be a key weapon for them during this tournament, whereas Arsenal/United lack such a player.
We all know how deadly Lewandowski can be in front of the goal. We have seen him score hundreds of goals for Bayern Munich and also score tons of goals for Barcelona this season.
So far he has scored 13 goals in 14 matches for them in the league, which is a pretty stellar stat.
I think Barcelona will win the match against Manchester United and progress to win the tournament.
Well after the jesus injury, I do agree that it would be a lot harder for Arsenal to win the tournament as well. I am not saying that it would be impossible, but it would be a bit harder than usual and it would be a bit more difficult.
I do agree that they do have a big chance, between Juventus, United, Barcelona and Arsenal, these four teams are the big clubs that could have a chance at the title but aside from them I am not sure if there are any teams that could win the title and it could be quite difficult to achieve. Long story short Arsenal is not the biggest candidate to win, whoever wins out of United vs Barcelona will be the biggest chance to win, but Arsenal is not too far from it neither.