Talismanic forward Cunha departed for Manchester United this summer, after scoring 15 Premier League goals last season and playing a big role in Wolves staying in the Premier League.
Arias arrived from Brazilian side Fluminense this summer in an initial £14.7million deal, but he has so far struggled for any great impact in the opening games of the season.
When asked about Arias' struggles, Pereira insisted the Colombian needs time to adapt and it is unfair to compare him to Cunha.
He said: "It's normal. It's not only about the Premier League, it's about the team-mates, it's about the system, it's about what he can add with his qualities to this team.
"But he has a lot of qualities.
"In the second half (against West Ham), I saw some qualities that I saw in Brazil when I played against him.