Minutes into practice at Scotiabank Place Wednesday afternoon, Carolina Hurricanes coach Kirk Muller was barking at his players to pay close attention to opposition defencemen rushing the puck. “Especially tomorrow,” Muller said in a voice loud enough to be heard well up in the seats, referring to Thursday’s game against the Ottawa Senators. No wonder. It’s the Erik Karlsson factor. Karlsson, the slick, slight and shockingly swift defenceman who “could be the best player in the league,” according to Senators coach Paul MacLean, hasn’t taken a step back since winning the Norris Trophy as the league’s top defenceman during the 2011-12. Indeed, Senators fans and opponents are seeing even more of him since the lockout ended and the National Hockey League resumed. It’s not just about the points — Karlsson ranks fifth in scoring among defencemen with four goals and four assists in 10 games — but about the control he’s having on the games he plays. Karlsson is seemingly everywhere: in his own zone, the neutral zone and inside the opponent’s blueline. He’s the quarterback of the power play and, in a new development, is also killing penalties this season.