Alex I think the dip in season form was from playing in Euro Cup and also Italian Cup. It always seems that the first couple years I get into that or Champs league. It's cause you really don't have depth on your bench yet to run all those games, so I usually tend to either do one of two things. If your team isn't great to go deep in the bigger tournament to toss those games (or at least rest some starters from time to time) to keep them in form for the league play to try to finish to make it back the next year (money is better there than in Serie A). Or what I do is to only play reserves for the Italian Cup (normally what I do), pick the league games you can rest some starters in, so you can still make a push in the Euro Cup or Champs league, and still try to push for either top spot in Serie A or a deep run in the tournament.
Which is why in my save I hardly ever won the Italian cup until my team was amazing cause I was more worried about Champs league and finishing first in Serie A. Italian cup was just extra if I won it, and there was plenty of times I got knocked out in my first game cause of playing just reserves.