We can't say the results they got in La Liga are not important and they just focused on the champions league because if they lose the La Liga games and lose the place in the second position of the league they will not bad atmosphere in their team because these bad results and we can't expect to see them winning the game against Macnshter City like that.
The Champions League is something special for Real Madrid, so I think some people will definitely believe that Real Madrid will have no problem against Manchester City in the Champions League even if Madrid's performance is not very good in La Liga. Basically I don't agree with that opinion, I mean when a team is in a bad condition, especially regarding performance, then they must have problems that will impact the next match.
Real Madrid have final against Osasuna in the Copa Del Rey today, so this might have an impact on the first leg of the Champions League. If Real Madrid manages to win the Copa Del Rey, then of course the team's confidence will get better ahead of the match against Manchester City. On the other hand, Manchester City is also in its best form after securing the top of the standings by 4 points ahead of Arsenal, so I hope the match between Madrid vs City will be very spectacular to watch.