If a match is held between AC Milan and Real Madrid, then Real Madrid will field players from the bench to show their strength, while AC Milan will consider Real Madrid as a big opponent and enter the field with their strong XI. Hence, such matches usually see relatively weaker teams winning against stronger opponents.
When it comes to friendly matches Real Madrid always look unserious amid the the weak teams bring them down which most of people will think that the team is not longer strong, and is not like that this is there nature of their playing if is not a really league, if not who is AC Milan to beat Madrid.
However, AC Milan's win over Real Madrid certainly gave them a boost of confidence that will come in handy when they start playing in the main stage. Seeing Real Madrid performing poorly in the pre-season matches, there is no reason to think that this team might not be able to do well next season. Be patient and wait for the season to start, surely Real Madrid's performance will make you happy.
AC Milan win against Real Madrid in the pre-season matches doesn’t means that they can able to compete with the Real Madrid next season, honestly Madrid can surprise alt if of people with how they will perform against any of their opponents by performing very well; because this is just pre-season matches so AC Milan should keep their boost confidence and wait for the really season to arrive.