Historical Tackle Data
Pro Football Reference only contains complete defensive tackling data back to 1994. Recordkeeping for tackles before 1994 was spotty and inconsistent, which can lead to misleading numbers. For example, some teams only tracked solo tackles, some gave multiple players credit for a single tackle, some didn't track tackles at all, etc.
For players we do display tackle statistics for from earlier than 1994, all tackles are listed as "combined," with no distinction between solo and assisted tackles. As our glossary entry states, they should used "for amusement only."