I don't know what your assumption is to make real sociedad the favorite to win this season. Although that is not impossible in football but in the Champions League, We know that other team still dominate the Champions league as favorites to win, Such as bayern munich, Manchester city and also real madrid. I will not refer to the improvement in performance of a team in the group phase and that is a strong reference that they will be able to become one of the teams included in the ranks of team that are candidates for winning the title. In fact, I think that psg will be able to stop real sociedad performance in the round of 16 because psg is more experienced in the Champions League and also has a better performance compared to them.
You can see the strength of other teams such as Bayern munich, Real madrid, which are able to perform better this season, Even these two teams are not only strong in the champions league, They also appear impressive in the domestic league. Therefore, I am sure that Real Sociedad will not be able to go further in the Champions League this season.
Real Sociedad being able to overcome the group stage hurdles and thereafter advancing to the last 16. Sorry to say but it'll only be in the widest of dreams that Sociedad will lift the UCL trophy this season. They're not so much of a good side neither are they a bad side. They've currently not just got what it takes to be the champions.
There are still teams far better than them in all aspects, doing exceedingly well and even making extra efforts than Sociedad makes. Yes anything can happen in football but there are some fates that have been envisioned out. Maybe they'd scale through to the last 8 but the odds are very much minimal. This stage of the contest isn't a joke as all teams are in their best, they've got now till the second week of February to prepare for their encounters. Let the best team advance into the next stage.