James Bettcher decided to become a homicide detective last week. While the Cardinals were off, the defensive coordinator tirelessly searched for answers that were killing his defense. He reviewed all the evidence, identified the motives, and ultimately identified the biggest suspects. The main culprits to a 3-4 start, he announced on Friday, have been the Cardinals’ ongoing inability to stop teams on third down and failing to force turnovers. Let’s just focus on the latter for now because that is clearly the easiest to hurdle. Interceptions are one thing, but all it takes to gain separation of the football from a ball carrier is a will and a want. Violent collisions help, but so does playing to the whistle, hitting with purpose, and going after the ball with a vengeance. You can poke, punch or strip or do all three to meet your objective. “There’s two parts to it,” Bettcher said. “Number 1, there’s no strip without a strip attempt. Certainly, you’ve got to have strip attempts to have the ball pop out. The other thing is just collisions on the ball carrier. If you go look at all the fumbles through the course of the National Football League, in most cases, ball carriers aren’t just dropping the ball. It’s contact at the point. It’s knocking the ball out.