Funny how we all know what "unsung hero" means, but few if any know where the idea comes from. I would argue that the first "sung" heroes were from Homer's Iliad and the Odyssey. I think most historians agree those sagas were originally an oral and not a written creation. "Unsung" is a word we owe to Shakespeare, who was the first known writer to regularly stick that "un" at the beginning of a word and thereby vastly increased our vocabulary.
Given the above, there are literally no unsung heroes on this Sox team because every single player is discussed endlessly and especially when they do something well in front of the NESN commentators and the Boston press in general.
Nevertheless, the word "unsung" has a lot of connotations and in the context of the thread title entirely appropriate to invite discussion about players who get less press and less appreciation but who nonetheless contributed to a remarkable, maybe even historic Sox season.
I would like to take that one step further and recognize those who perhaps deserve to remain unsung, and would begin with Pablo Sandoval and Hanley Ramirez because I think their departures--even though the Sox are still paying them lots of moola--helped this current team. We needed them gone and DD (and this year Cora) deserve our thanks.
I would also nominate Swihart and Pomeranz because for most of this season I for one thought that were wasted slots on the roster. Swihart lately has made DD and Cora look like geniuses even though he is still a bit player. Yesterday was a perfect example of Cora's genius and Swihart's stunning versatility despite having played the fewest games of anyone on the roster all year. As for Pomeranz, I still don't like him, but give him and Cora credit for trying to contribute from the bullpen.
All that said, I basically agree with those above who singled out Leon, Barnes, Johnson, Velazquez and maybe Holt. But especially Leon.