That article mentions Sherman was beaten only once in primary coverage, and that his grade comes from 2 coverage penalties and 2 missed tackles.
The penalties are going to happen when Sherman rides the line. As far as missed tackles go, it's true he isn't looking the same as last year. But he's looking the same as Earl and Wagner to me.
Earl has done his dive in headfirst no-arms routine once per game at least. Wagner has also been missing tackles.
Our stars have all looked sub-par. I worry about Sherman as much as I worry about Earl and Wagner, which is to say I don't think any of them are in any sort of significant decline, but they all need to pull their heads out and tighten down the focus. Coverage will improve with Kam's return, tackling shouldn't be crap even if Kam is relocated to Mars.