Btw, Inter in the past 2 years has done a some good business, they practically made a respectable team with players exclusively signed these years. Of course they spent a lot this summer, and they did some dumb shit before (like Kondogbia or Jovetic).
They had 2 good players before: Handanovic and Icardi. Last 2 mercatos they added:
Murillo - 8M (steal - he's probably worth 3x now)
Miranda - 4M for 2yrs loan + 11M (absolute steal - can't believe Atletico accepted this. One of the top CBs for me)
Perisic - 16M (he's a good left winger. Didnt fancy him, but the more I see him play, the more I like him)
Candreva - 22M (good pure right winger)
Banega - free (very good signing)
Joao Mario apparently was overpaid for 40M, but I dont really know the guy. Seems good. Gabriel is an interesting signing, like Caprari and Manaj. Eder is a good squad player, as is Brozovic, who was cheap.
Now, they actually have a team. Kondogbia has been horrible, but part of is probably because of the mess the club has been. In an ordinated team, he could be a good DM.
What they don't have is fullbacks. Their fullbacks are disgusting. But they do have Di Marco, the greatest prospect in a long time for the LB position. Kid could be a stalwart for Italy at the position for years to come.
If they solve their fullback problem and get some depth for the midfield and defense, they will be very competitive.
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I wouldn't say Napoli have reached their ceiling, they are a pretty young team, Sarri is there to stay and in the summer their team might only get stronger, they probably will loose Koulibaly, but I can't see any other departures. For me they seem a little bit more focused on the long term than we are which worries me a little in regards to our future, in a year or two we might have a serious competition.
Thing is, they will be a threadmill team. The ceilling is the limits on salaries. They actually kept Cavani and Lavezzi for more time than I expected.
Jorginho and Allan are 2 players that fit very well for Napoli's size. If Zielinsky, for example, explodes, I don't think they can keep him for long. Milik the same. They have space for one or two top player salaries, but not for more than that.
They've hit the jackpot signing guys like Allan, Jorginho, Goulam, Mertens, Callejon, who are good to very good players and thus Napoli can keep. A little bit better, they be top, and Napoli would have to sell them, and start all over again. These are guys that would be excellent rotation players for us. But really good enough to start consistently.
I just dont see them becoming much better than they are now, not without more revenue. They are doing something close to the best possible job with the revenue and appeal they currently have.
The only way to scape this would be regularly performing well in CL. If they manage to build some name, like Dortmund did, they could grow.
But as of right now, I already see them as a championship threatning team. Juve will have to be solid as hell.