Wingers can get away without defensive responsibility down low in their own zone, where body position is extremely important. Being so light, Pettersson would likely get pushed aside, and not be any kind of impediment to his opponents. could you imagine him trying to pin a 200 pound man to the end wall, and also keep that man from moving to the front of the net? With the puck, I'm sure the kid is amazing. Without the puck, as a center, his lighter weight and lack of strength would make him a big time liability in his own zone.