Seferovic told reporters: "There are new rules, for example, we have recently had to wear shoes when eating. He is a different manager with different ideas.
"Mr Petkovic is a very good coach who knows what he wants. But I think we'll need a while to adjust and to play how he wants. But I'm in shape, I feel good.
"When I play, I go into the game the same, no matter what the opponents say. We have respect for England. But we must not have too much respect and play our game."
Petkovic takes charge of his first game later today against England.