Arthur is Neymar's mate at the Seleção. So the friendship is needed. I don´t think he will be like Neymar however, in character. He NEVER was. And Neymar ALWAYS was like that. Neymar was 17 and there was already brazilian coaches saying the media was creating a "monster" and even there was a spat with a Santos coach that ended up costing the Santos coach his job.
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He can score too. He had started getting closer to the box this year when the coach asked him to do so. Scored 4 goals from March to June, as he returned from injury after 100 days without playing since the Libertadores final against Lanús (Arg), and then there was the World Cup and soon after he left for Barça.
He played 18 matches for Grêmio, from March to June before the World Cup.
As you will see, the goals scored this year, one was a possession and dribbling in a very tight space in the box, without barely moving, after getting a low cross.
Another was a goal kicking the ball on first touch.
The third was a goal running half the pitch after getting a shoulder pass from Jael. More importantly... it was in the biggest brazilian derby, the Gre-Nal.
The fourth was a nice, curved, low shot goal on Santos, for the brazilian league.
imho, as Arthur gets to know his mates better, and starts seeing them as mates, instead of superstars from TV, he will feel more confortable in trying to score himself, or a long pass, etc.
back in the 80s or 90s, he would have played with and against some of the best in Brazil. Nowadays, not so much. So you have a good opportunity to dribble or shoot at goal... but then you see Messi and Suarez and Coutinho upfront. You probably think "gee, I am only arriving here... if I miss this, when I had a chance to pass to god-II, he will bash me, and the fans will bash me... I will play it safe and pass".
Attackers are usually different. They are brazen and risk takers by nature. But midfielders and defenders will be more conservative and cautious.