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.
First of all I should give some information about Jesus' injury. I have seen on some news sources like Jesus' return will be in early March. If this is true than it is really sad news for Arsenal.
However Arsenal have already proven how strong they can play in Jesus' absence also. Jesus couldn't score any goal after the last match he did on October 1. But Arsenal still didn't get affected by that in a negative way. They still continued to get very positive results by scoring many goals in total. They lost only once which was in a Europa League match. They won nearly all of their Premier League matches in this period of time. This is a proof for how strong they can play as a team even in this kind of situations.
Therefore I'm still seeing Arsenal as the biggest favourite here also.
He has successfully knee surgery several days ago and still struggling to recover his injured but there was no exact information regarding how long he cannot play for Arsenal that some of people says 1 month or more than it and admitted or not Jesus is the key player for Arsenal and losing him will have bad impact for Arsenal performance but there are still few months remaining before round of 16 started so maybe he will be recover before February so there is a chance for Arsenal to playing him
This season Arsenal don't have any players who can be suitable to replaced his position and i have to say there were no players who had equal quality to him for forward lines so Arteta have to find best solution to solved this issue and this is the risk why world cup is held in the middle of a regular competition because the players possibly can got injured because of tight schedules and i think other clubs might be will suffers the same consequence