Roosters destroy Port Adelaide in second half North Adelaide midfielder Cohen Thiele dishes out a handball under pressure from Port's Matthew Rose. Picture: Dean Martin. NORTH Adelaide found its killer instinct by exploding after half time to demolish a woeful Port Adelaide by 73 points at Prospect on Saturday. The Roosters kicked 12 goals after half time and conceded just two points in a win that puts them a step closer to securing a top-three finish. "Prior to last week against Glenelg we hadn't seen that (killer instinct) in the group so to follow it up again today was terrific," North coach Josh Francou said. For the playing group to keep persisting, with a relentless attack on the footy and the body, it creates pressure and we know if we get that right, the rest of our game will come. I was a little bit worried in the first quarter when we couldn't get any scoreboard pressure, then to go into half time two points up and come out in the second half and blow the game open was pleasing. While so often North Adelaide victories are built on stellar peformances from its big-names, yesterday's win was due to solid contributions from some of the workhorses who often miss out on the accolades. Midfielder Ben Williams, playing just his 16th league game, was outstanding and capped his game with two last-quarter goals, most of Jay Shannon's 24 touches were contested and Jake Keller denied Graham Johncock front position all day and kept him goalless. For Port Adelaide, it could not have been a worse result after coach Ken McGregor described last week's loss to Sturt as its most disappointing of the season. "We've gone backwards since the bye and it was a pretty disappointing game, especially the way we gave in in the last quarter," McGregor said. We started losing contested ball and they're (North) so skilful that if they do get it out to their runners they're going to hurt you. It reminded us of how we were playing very early in the year, that was the most disappointing aspect and we've got to stay united if we want to get any better. Ben Newton and Sam Gray battled hard in the midfield and Zane Kirkwood, Steven Summerton and James Watt had their moments, but it was hard to find a Port player who won his position. The biggest worry for Port was its inability to stop the onslaught and what should have been a tight contest after an even first half, became a 12-goal hiding. North dominated the first quarter, inspired by hard-acts from Chad O'Sullivan who ran 50m to lay a shepherd and Williams who went back with the flight of the footy in defence - but couldn't capitalise on kicking with the wind. A huge goal to Kory Beard early in the second term gave the Magpies the lead but not for long as Lewis Johnston ran onto the ground from the bench and got the quick reply. Two goals in two minutes - both from outside 50 - to Tom Langford after half time got the ball rolling for North and it was never challenged thereafter. It seemed everyone got in on the act in the final term as the Roosters piled on another eight goals to romp away to its second consecutive 12-goal plus victory. BEST - North: Williams, Keller, M. Thring, Johnston, G. Thring, Shannon, Campbell. Port: Newton, Gray, Kirkwood, Watt, Summerton. SCORERS - North: Johnston 3.2, Thiele 2.1, O'Sullivan, Langford, Williams 2.0, Gordon, Blee, M. Thring, Ryswyk 1.0, Shannon 0.2, Clinch, Miles, Kangur 0.1, rushed 0.1. Port: Thurgood 1.1, Meiklejohn, Beard 1.0, Young 0.3, Kulikowski, Hoskin, Summerton 0.1, rushed 0.1. At Prospect Oval.