I watched the Sanchez sack in slo-mo instant replay a few times.
There was a stunt between Ferguson and Slauson's men. Ferguson recognized it and was trying to pass his guy off to Slauson - but Slauson didn't notice the stunt and had left his spot to help in the middle. At which point Ferguson stuck with the inside guy, which was probably correct, and drove him across. But the stunting guy had a clear shot at Sanchez. IOW, this was caused by Slauson's mental mistake (and coupled with Sanchez possibly holding the ball too long).
From what I saw in general, I think Powell did a very good job blocking.