I feel like if you can manage it, an Andrew Benintendi extension makes a whole lot of sense right now. He’s coming off a career-worst season that was ended early with injury, so this is the lowest his value likely will ever be.
I don’t know what’s wrong with him, but I also believe he will be better. Eventually. Get him signed, long-term and relatively cheaply while it’s still possible, and avoid the uncertainty in future arbitration salaries and buy out a few of his free agency years.
Sox management probably have the best idea at what is going on with Beni this season. If they sign him to an extension, it means they really think this year was a fluke. Once Pedroia is off the books, they could hide a bad contract if Beni goes south anyway. It also is a fine balance between years and AAV. They shouldn't go crazy like an 8 year deal.