Berra, 24, believes his move to the Premier League from Hearts has brought about a big improvement in his game.
The Scottish centre-half has earned a call-up to the national team having impressed in recent appearances at Molineux.
Now preparing for the friendly with Japan, he says his turn around in form is largely down to Mick McCarthy.
"There are things he wants me to do and ways he wants me to play," said Berra. "But if you've ever watched us you'll know we're not a defensive-minded team.
"It's maybe a bit different to the way I played under Csaba Laszlo at Hearts. We were more defensive and counter-attacking than Wolves are."
Berra admitted that the quality of opposition he faces at club level has made him concentrate much more on the pitch.
"You're playing against strikers who cost between £10million and £30million, so obviously every team is full of quality players," he added.
"It's only going to improve me, because every week I'm playing teams who bring quality players off the bench.
"One thing I've learned is that you can't switch off for even a split second or you'll be punished."