For Milan this season will probably not have a happy ending and certainly not a comfortable one in the last three games. Even Lazio got lucky now that AC Milan failed to win again or otherwise they could have gotten into trouble as well. Now it seems that the first four ranks are almost certainly taken by the top four as per current standings in the table. I wouldn't expect any changes from here on and for AC Milan the next seven six days could be very ugly if they get eliminated from the Champions League and then Lazio perhaps win their game in the Serie A or even tie it, the dream to qualify for the biggest European club tournament will also slowly but surely come to an end.
Yes, Milan will most likely end the season very disappointing. I saw that Milan made quite a few unforced errors which impacted their targets in Serie A. The Rossoneri's move will be even tougher because they must allot their focus to the Champions League. I saw that Pioli was very nervous in preparing the team when faced with such a precarious situation. He should have maximized the match against Spezia and not save a number of his main pillars. In the Champions League, Milan's chances are very slim, although they are still optimistic that they can catch up with Inter. I predict that Milan will fall in Leg 2 and the steps in Serie A will be tough in the remaining three matches.
Unforced errors, I haven't read that before in soccer but it is a good example to describe how Milan performed recently. It is the problem of many teams towards the end of the season. They play decently at least, often times even spectacular soccer for many games and you think that they will be safe in the Champions League qualifiers, and out of a sudden their performance dumps into oblivion and you don't even recognize the same team is playing on the pitch right now. A lot of people say that players are tired and what not, but that would apply to all teams equally. Now when they mean tired also in terms of the mental condition, I think that is a possibility. Similar to a burn out when the pressure got too deeply into their heads and they lack focus more and more over time. That could be a possible explanation.