Odds are against him? How, and in what way? Care to elaborate?
Statistically.
If Barca/Rm buy 10 players like Saviola, Quaresma, Simao Sabrosa, Gerard Lopez, Deiberson, Rochemback, Denis, Gomes, Paco, Digne, Frenkie, Umtiti, Dembele, Malcom, Arthur, Halilovic, Odegaard, Kubo, Donny, Vinicius, Rodrigo, Drenthe, Gago, Diogo, Cassano, Odriozola, Llorente, Theo Hernandez, Illaramendi...
Statistically 2-3 out of 10 will turn into a starter material or reach crazy expectations (Dembele, Robinho, Saviola, Quaresma, Sabrosa, Geovanni, new Messi Halilovic).
Required quality is too high.
Guys are mentally not ready.
Barca and RM can't develop players slowly. You need to perform right away.
New country, new league.
Lots of money, popularity, parties, girls, alcohol.
I wasn't talking about Donny in particular, but about any young 18-22 years old (especially foreign) player coming to Barca/Real, regardless of his previous club career.