but many of his tackles have been downfield in pursuit and plays the safeties or corners should make.
I hear this a lot. "Yeah, he's getting lots of tackles but they're all a good distance from the line of scrimmage." So are we supposed to discount those tackles for some reason? Is he likely to lose his job for making tackles that safeties and corners should be making? If anything this is better for an IDP than making all their tackles near the line of scrimmage. Accumulating stats is all about opportunity. If they're making tackles further away from the line of scrimmage, their opponent is that much closer to getting a first down, and three more opportunities for the IDP to make a play. If they're making all their tackles near the line of scrimmage, the offenses drives are more likely to stall, sending the IDP to the sidelines.
Unless your league's scoring system weights tackles based on their proximity to the line of scrimmage, I fail to see how this is a negative.
It's not necessarily a negative and I didn't suggest that the tackles should be discounted. I call it the Ronald McKinnon Corollary. But it's important to note for a number of reasons. As you suggest, in the short-term it is clearly better for the team (and IDP) in question.But it's absolutely worth noting for the long term. It's up to you to decide whether the player is making all these tackles because the scheme allows him to be the best pursuit player and highlighted playmaker or is the most talented (Keith Bulluck) or if there is an identifiable reason that he is "picking up the scraps".
In this case, you should be concerned about the likelihood that Howard continues this pace over the long haul. Michael Huff will take some of these tackles moving forward. And should the Raiders upgrade the defensive tackle unit or corners over the next 12 months, Kirk Morrison (who, by scheme, should be the highest tackler) and the improved corners will take those tackles.
If you don't pay attention to why a player who seems to be outpeforming his scheme or surrounding cast, you might end up with a player like Demorrio Williams. If you play in redraft leagues, that's no big deal. But those who either got stuck holding the bag or flipped Williams for top dollar this summer in dynasty leagues know differently.
In the case of our hero, Ronald McKinnon, it was some years (and Pat Tillman's presence) before replacement level talent resulted in replacement level stats.