Vieira left Porto for the Gunners last week.
Fernandes said, "I welcome all Portuguese players who go abroad, I hope he can shine to the fullest, except against me.
"Fábio has a lot of quality and has been demonstrating that, whether at FC Porto or in the under-21s, he has had good numbers and good performances. I hope he succeeds like all the Portuguese out there.
"We have to start valuing what is ours and I hope that Fábio manages to be as good as possible, despite hoping to stay ahead of him!"