In today's post-steroids world the expectations for and value of (power) bats needs to be adjusted. A guy like Cespedes has warts, but brings things to the table that have become scarcer. Look at the Cy Young landscape. Lots of quality candidates with ERAs that would have looked silly 5-10 years ago. Pedro's epic year saw him post similar ERAs to what the leaders have in the heart of the steroid era. What made Pedro's year special was that his peers were so far behind him. Now that ERA is much easier to attain.
So in that light, a return like Cespedes makes sense.
Lester will be resigned by Boston. That is my prediction.