This is a fairly succinct post, but in all the articles coming out about the poor job the replacement referees are doing, not enough of them are talking about player safety with specific examples.
The clearest one for me is the late hit Alex Smith took on his 4th quarter slide, and it was to the head. Late hits are just not getting called across the board and it seems the NFL is refusing to fine players for dangerous play after the games regardless of a flag being thrown or not like they did last year. This is probably in attempt to keep attention being drawn to the problem.
Think about how much aggression is on the field, take notice to how there are more late hits, scuffles after the whistle, and frustration all around, and it seems eventually there will be an incident that will mar the season entirely. Hopefully the 49ers are not involved.