I've noticed quite a bit this year that Simmons hasn't made plays I'm accustomed to him making. Not that he's been bad, he certainly hasn't. But at the same time, he hasn't been awesome either. I thought maybe I was just imagining things, but then came across this article on fangraphs.
Link
The plays in this article are extremely difficult. But I've noticed others that easier that were not made - including that two error (one charged) game in St. Louis.
Anyways, I do hope this is just a slump, and last year was not a crazy aberration. We are certainly paying him to be a defensive wizard.