Duchene was lackadaisical on the defensive end and just didn't get fully burned, he also had like a 65% OZS and somehow ended up with a negative corsi for his first 2 games with Ottawa.
He wasn't that good defensively. He should be better, but he just hasn't yet. No harm in admitting that because his history says he should gel with this teams style (low giveaways, high takeaways). May take some time to kick some bad habits he got away with in Colorado.