Most IDP fantasy scoring systems give more points for tackles then assists. There are two types of tackles, solo and shared, but my guess is that most fantasy sites can't distinguish between the two given the data feeds they rely on (I fairly sure NFL.com can't, for example).
When two guys are marked as having split the tackle the default scoring is to give the first guy a (shared) tackle, the second guy an assist. This default is changing for next season. The new default will be for both guys to get assists and neither guy a shared tackle. The data entry folks can override the default value but in practice they rarely do.
This will likely decrease the IDP value of certain players, primarily linebackers who play home games at stadiums that tend to award a lot of split tackles. Using a hypothetical scoring system of 1 point for (any kind of) tackle, 0.5 points per assist here are the top three guys who would be affected:
Jerod Mayo would have scored 19.5 fewer points
Paul Posluszny would have scored 18.5 fewer points
Stephen Tulloch would have scored 17.5 fewer points
Generally this won't affect players who get most of their split tackles on split sack plays. The overwhelming majority of split sacks are currently being scored as assist/assist. The change to how split tackles are being scored on regular tackles is being made so that it matches how split sacks are being scored.
When two guys are marked as having split the tackle the default scoring is to give the first guy a (shared) tackle, the second guy an assist. This default is changing for next season. The new default will be for both guys to get assists and neither guy a shared tackle. The data entry folks can override the default value but in practice they rarely do.
This will likely decrease the IDP value of certain players, primarily linebackers who play home games at stadiums that tend to award a lot of split tackles. Using a hypothetical scoring system of 1 point for (any kind of) tackle, 0.5 points per assist here are the top three guys who would be affected:
Jerod Mayo would have scored 19.5 fewer points
Paul Posluszny would have scored 18.5 fewer points
Stephen Tulloch would have scored 17.5 fewer points
Generally this won't affect players who get most of their split tackles on split sack plays. The overwhelming majority of split sacks are currently being scored as assist/assist. The change to how split tackles are being scored on regular tackles is being made so that it matches how split sacks are being scored.