fact Atletico and Manchester United have never played in any tournament so far, so there is no head to head record for this match. History is not an exact benchmark, because of the different situations, conditions, squad and many other factors that will certainly make the past not the same as what will happen today and tomorrow. We just need to make sure the team's recent performances are clear, Atletico is in decline and vice versa, Manchester United which keeps getting better then at least it promises something good for Manchester United and not just about 1 or 2 players.
Comparing these two teams, I think Manchester United is a strong team. Atletico Madrid is not playing well. Their position in La Liga is also very weak. They have lost their last 4 matches in La Liga. Lost form in a very bad way. Atletico Madrid have no hope of winning the La Liga title. However, despite the improvement in performance, they will not be able to beat Manchester United. United are a very strong team.
Not as strong as imagined, if Atletico really come back and recover 100% then I would say Atletico have a better chance. The situation is different now, although Manchester United without Ronaldo I believe Manchester United still has a chance to win. I only consider that Atletico's condition which continues to decline is very different from Manchester United, conditions like this are clearly very unbalanced and I'm not saying Manchester United are a very strong team. It's about what kind of opponent they will face, because for me Atletico in the last few seasons had a good defense but this season they have been declining.