Advancing from the group stage is the big challenge in UCL because of the new format. Any club that is able to qualify from the group stage will become more focused with their matches because they have the advantage to qualify to the next stage if they win their opponent. It's from that stage that one can start to predict which of the clubs will be the favorite for the Champions League title this season.
It is very obvious that after the group stage is the decisive stage of the champions league, where we get to see teams who have passed through the first stage of the competition and heading to the knockout phase. I just know that the more they go higher in the competition, the more they face difficulty because of the nature of the competition requires you to be more super creative. Base on the performance of the group stage matches in the competition, that is how we can better tell which teams will stand a better chance in the competition going forward and those that have the higher tendency of making it to the next round and eventually the final if they keep up with their good form.