Reinier had been part of the Copa Libertadores winning Flamengo team, although as was the case with both Rodrygo and Vinicius Jr, there is a significant amount of development which must still be accomplished before he is ready for LaLiga Santander.
"He has surprised me at 17 in that he always chooses the correct option," Filipe Luis explained in an interview with MARCA.
"When he has to pass, he passes, he plays with his head up.
"It really is a great signing, I congratulate Real Madrid."
Former Atletico Madrid fullback Luis believes the talent is there to make Los Blancos' investment worthwhile.
"He isn't 100 percent ready," he added.
"He is 17 years old, but has potential and a great future.
"Nobody is ever ready for a leap so vast at that age, but in the future he will be a great signing."