Body checking is overrated, and out of style in any event. The main thing is to use your body by placing it in between your opponents body and your own goal. Koivu was superb at this, and at using his big body to influence games. It's one of those things you don't notice if you are watching on tv, rather than in person. He was a terrific all round player who spent his prime with mediocrities and under a defense first system, like Barzal is under now. That is going to deflate offensive numbers.