After a stuttering start to his Molineux career, former Jambos skipper Berra has helped his new club keep a hat-trick of clean sheets to maintain their three-point lead at the top of the Championship.
And McCarthy believes there is even more to come from the 24-year-old Scotland international, who he signed last month.
"He said it himself: judge him after five, six or 10 games," McCarthy told BBC WM.
"He's been a really good addition, he's been terrific.
"And when he's had a pre-season with us and he knows a bit more about us, he'll be even better."
Wolves 8/15, Draw 11/4, Charlton 6/1