Yes, I think this is the right moment for Barcelona to prove they can still go further in the Europa League to correct their mistakes in the Champions League and Europa League last season. Even though at this moment Barcelona had a pretty difficult opponent too, but because Manchester United's performance seemed to be declining, Xavi should have been able to make Barcelona win.
Because if Barcelona still lose this match, then I think Xavi is just making Barcelona focus on La Liga.
Barcelona can do it if they can beat manchester united in the next 2 weeks. Nothing is impossible for them if Barcelona perform better against Manchester United. But their opponents in form in the premier league what hinder them a little from going further. Dembele is still injured, I think this can interfere with their game a little in the match.
Manchester United also lost Eriksen due to injury, maybe this will be a weak point for them because Eriksen has become an important player in Manchester United's revival this season.
I think these players can recover as soon as possible and both teams can appear with a perfect squad when this game starts.