If you continue to be proud of history without achieving success after that it will be a story that is not so interesting and this happened to Manchester United because for the past few seasons they have been a very weak team. In terms of quality, the two are not that different at this time and it may be difficult to predict who will win the match. But Manchester United will travel to Real Sociedad's home ground and the result of the first leg will be enough to determine the steps of both teams to qualify for the next round.
The defeat from Barcelona is not a reference because they did face a much stronger team, but look at how Manchester United performed in the Premier League and it does not at all show the quality of the team as a candidate for the title.
The difference for United is that they still make a good chunk of money even when they are not successful. That kind of money makes it possible for them to be good at any given season, we haven't seen them be that good for a long time, we haven't seen them win a title in many many years, but at least we have seen them get better, because they have money.
Every single year, they are capable of spending 100+ million if they want to, not that many teams in the entire world can do that, I would say there is probably a dozen teams or less that can spend 100+ million for 10+ years in a row if they want to, doesn't mean they will, just means they can if they want to. So that makes them a team that has a history, but also a potential too.