19-year old Matheus played alongside fellow Brazilian Leonardo in central defence in this week's 7-2 friendly win over UCLA and he was praised by his compatriot.
"It's easy to play with him because he's Brazilian, and in Brazil there's a different style," said Leonardo. "There's a line of four [in the back] here, but in Brazil, the two wingers move up forward and the two center backs stay back more. He's played well. He's only had two or three days to adapt himself over here, and he's done OK."
But head coach Arena was more tight-lipped: "Don't have any lasting impression [on Matheus Ferreira] at this point. It's just wait and see every day and see what he looks like.
20-year old midfielder Marquinho did not play on Wednesday and Arena insists the club is simply casting an eye over him.
"Again, just in for a couple days. We'll see as he moves forward," he added.