49ERS SQUAD SHOW: Insights From 49ers Chargers Joint Practice, Kaelon Black EXPLOSIVE

The San Francisco 49ers participated in a joint practice with the Los Angeles Chargers yesterday, and Kaelon Black looked explosive in his reps against Jim Harbaugh's defense. Kyle Shanahan provided an unfortunate update on Mykel Williams and his timeline to return from the ACL injury he sustained last season. Plus, the San Francisco 49ers' defense looked suspect against the high-powered Los Angeles Chargers' offense. Should this be a cause for concern for 49ers fans?