there are different rules for the cl and the serie a. what i wrote applies for the cl list. in the cl, you have:
- 4 club trained slots: marrone, marchisio, 2 remains unfilled
- 4 italy trained slots: buffon, chiellini, barza, bonu (or any other 4 made in italy players)
- 17 "free" slots: 17 of neto, benatia, rugani, sandy, alves, licht, evra, khedira, pjanic, asa, lemina, hernanes, sturaro, dybala, mandzu, zaza, higuain and pjaca (18 players without cuadrado)
so you have to exclude a player from the current squad, even without buying cuadrado.
in the championship, it's easier to comply to the rules as you can move rugani into a club trained spot, include pjaca as an u21, and you're fine.