"Karlsson has been compared to Detroit blueliner Niklas Kronwall.
Karlsson needs to get bigger, but those who have seen him play say that he "hits like a Mack truck" and has tremendous offensive skills that are going to help the Senators' power play down the road. "
- Ottawa Sun (Bruce Garrioch)
"He led all defencemen in points at the U-18 Worlds grabbing 7 assists in 6 games. He was selected as the best defenceman in the tournament. In 38 games with his junior club Frolunda, Karlsson averaged almost a point a game scoring 13 goals and adding 24 assists. His 68 PIM showed he may be small but is feisty. He also played seven games in the Swedish elite league where he scored a goal and registered a plus-2 rating. "
- USA Today