At this point we don't know if either of the trades are "wins" in a vacuum; but in the context of the Red Sox offseason and putting the rotation together I"m encouraged by Cherington's approach. Signing Lester would have solidified the top end and made sorting out the rest of the rotation much easier; didn't happen, and the market Lester set makes it unlikely that the Sox will be able to land either of the other top FA SPs. So now if you're trying to bring in that #1 it may have to be via trade. As the Cespedes/Porcello swap shows, the impact of buying/selling from depth/scarcity can be overstated so long as the teams have a match (remember "they won't get anyone for Cespedes cos everyone knows they have to trade him"); however, you'd still rather not be trading for an ace with only two MLB starters in the rotation to begin with. Yikes.
So, plan B. By stocking up on Miley/Porcello/Masterson, they've got an actual rotation they could start the season with, including two innings eaters who look to be coming into their own as more than just innings eaters (Porcello + Miley), two guys who've had elite results in the past and could rebound with health (Buchholz + Masterson), and Kelly, who's still coming up to speed as a starter. If they stick with that, getting the innings eaters is particularly useful in offsetting some of the risk around Buchholz (health) and Kelly (stamina). And if they still want to add an ace, they've got flexibility to use the starters under team control in a trade package, or bump Kelly to the pen if Shields does take a short/reasonable deal. And while RDLR was a favourite, they've done it without compromising their prospect depth. I'm still miffed that it ever came to this with Lester, but that's a very solid recovery.
Moreover aside from what they did, it's worth noting they were reportedly a finalist for McCarthy, who looks to be signing for 4/48. Four years isn't ideal (and maybe that was Cherington's sticking point, who knows), but in this market, getting a guy who's been very, very good when using all his pitches and, despite the injury concerns, has put up over 600 IP over the past four years for $12m/year is a nice gamble IMHO. Shame it doesn't look like it'll work out, but I like the approach. (This officially concludes my McCarthy Advocacy Project 2015).
Edit: forgot the other positive; even if the high GB rate thing is just a coincidence, it gives us something to chew on.