Atalanta, Fiorentina and Lazio are likely to fight for 3rd place at best, because their 17 points gap is already quite large and here the gap is more serious than Milan's 7 points.
I think maybe you mean the fight for 4th place because Atalanta, Lazio, Fiorentina and even Bologna, As Roma and Napoli still have a small difference so they can fight for 4th place, but getting 3rd place is very far away, let alone catching up. Inter Milan and Juventus are at the top of the standings, AC Milan has really maintained their consistency so far as well as Juventus and Intermilan are unbeaten in their last five matches, that is a good job for a very consistent club.So far there are almost 6 clubs that are likely to be in 4th position at the end of the season, if Atalanta cannot be consistent then they will be easily replaced by the clubs below them, therefore the competition this season is also very tight besides the title competition at the top of the standings is also very tight in the fight for place in 4th position, talking about champions this season, it seems that the meeting between Inter Milan and Juventus in February will determine who deserves to be champion and fight for the Italian Serie A title this season.
