All the teams in the quarter-final round are very strong. There is no opportunity to think of any party as weak here. I think every team that qualified for the quarter-finals has the potential to qualify for the semi-final round.
You're right, other than that the level of motivation to reach the semi-finals for each club will be anything but it could even be that we're going to see an unexpected club qualify. For example, Chelsea, which is still in doubt, also seems to be a little difficult to predict, so Real Madrid is really wary of Chelsea players.
There is another thing that has caught the attention, namely Manchester City vs Bayern Munich which are considered to have strong defenses against each other. Both Bayern Munich and Manchester city are quite balanced in their strengths and could possibly end in a penalty shoot-out.