Here is a look at 18-19 y/o that moved to Europe and how they adapted to Europe, this are names that I remember there are much more than this:
James Rodriguez Banfield to Porto - Led Banfield as an 18 y/o to the Apertura 2009 championship being one of the most important members of the club along with Santiago Silva. Had a great Copa Libertadores prior to going to Porto scoring 5 goals in 8 matches, including some MOM performances. Was sold to Porto for 5 million Euros. His first few months at Porto were not so smooth but by mid year he had become a rotational player, had 24 apperances for the club 10 coming of the bench scoring 3 times with 5 assist. His 2nd year(this year) he's a starter and has been playing great so far with 5 goals in the league in 9 games and scored 1 goal in 5 matches in the UCL with 1 assist.
Javier Pastore - Starred as an 19 y/o for Huracan fishing second in the league, had 7 goals and 3 assist in 19 games. Was sold the following season for 8 million euros to Palermo. His first 6 months with Palermo were up and down he came off the bench and showed potential but didn't put it all together. The 2nd half of that season he picked up and started showing his potential more and more. Ended that season with 3 goals and 5 assists in 34 apperances(27 starts). His 2nd season he was much better, he started hot scoring 6 goals with 2 assists in the first 6 months. He ended that season with 11 goals and 5 assists in 34 league matches. He also starred in a great match against Milan in the Coppa, Palermo eliminated Milan. He was sold for 40 millions euros of so to PSG.
Alexis Sanchez Cobreloa to Udinese - Sanchez debuted as a 16 y/o for Cobreloa then as 17 y/o was regular in the Chilean league scoring 6 goals in 12 games. Udinese bought him for 3 million dollars. They loaned him to Colo-Colo, probably the biggest club in Chile, He spent the entire year at Colo-Colo, playing in two championships, and he won the two title as a 18 Y/o, info on these seasons is hard to come by but he scored 3 goals in 7 Copa Libertadores matches and scored 5 goals in 32 league matches the entire loan spell. Udinese then loaned him to Argentinian side River Plate, where he scored 4 goals in 34 games and played in 8 Copa Libertadores matches were he did not scored. He finally went to Udinese and his first season was a bit of a struggle and his 2nd season as well. He starred for Chile at the 2010 WC and followed that season with a great season with Udinese. he scored 12 goals and had 6 assists in 31 games. He also played great against Inter, Juve and Milan. He was then transferred to Barcelona for 26 million euros plus variables that could make the deal worth 36 million euros.
Kun Aguero Independiente to Atletico Madrid - Kun made his debut for the club as a 15 y/o, the youngest ever in the Argentinian top flight. Then as 16 y/o scored 6 goals in 12 league matches for the club. He then became the starter for the Apertura 2005 and Clausura 2006 scoring 18 goals in 36 games with 4 assists. Atletico Madrid bought him for an Argentinian record 23 million euros. His first season as an 18 y/o was up and down he started off the bench with some starts in between and then became a starter for much of the season but ended that season coming mostly off the bench and scored 6 goals with 3 assist in 36 league games(13 as a sub). His second season as a 19 y/o he took off and was the starter. He scored 19 league goals and 7 assists in 38 league games which included a great game against Barcelona where he scored twice, assisted one and won a penalty to win 4-2 over Barca.
Just a few names that came to mid of players that played in Argentina and came to Europe at a young age, I know there are more names just this are the names that came to mind. If he comes next season we have to be patient and have faith in him. It doesn't happen from the get go at smaller clubs imagine Inter?