c. I didn't because it was not part of my point. I simply chose not to. Based on what you just wrote, you are valuing Miley less than I am. Miley eats your innings and those are the innings Buchholz et cetera have to fill now. For the record, Miley (who doesnt pitch that well as you opined) had a higher WAR than Smith in 2015. 2.6 vs. 2.1. So he was 0.5 wins more valuable than Smith. You could interpret that differently, but for me it comes down to that stat.
I don't think you're taking into account the cost savings. The Red Sox shed $14 million of payroll. They can buy wins elsewhere with that. This is also a multi-year deal, and the wins Smith and Elias are giving you are close to free, because they are cost controlled. Unless you have a better option on the bench that you otherwise wouldn't play who can do better in the same innings, even 1 win from a $500,000 player is pretty good. Miley is moderately cost controlled -- if he gives the Mariners 5 wins over the next two years for $12 million, they will have done great. But it's only two years. After that, he'll get paid as a free agent, which means by definition he'll be paid precisely for exactly how the market values his likelihood to save runs. Smith will make $8 and maybe $15 million or so over the next 5 years. He doesn't need too many wins to prove a higher value than Miley (and, obviously, the more he makes in his arbitration years, the more value he would have provided). Even 5 wins over 5 years, and he's given more value than Miley is expected to.
I also don't think you're really grappling with the resources point. They had a surplus of starting pitchers. So, if you want to ask what Miley's value (using WAR again) would be next year, you can't just say "steamer projects him at 2.1 wins, so that's what the Red Sox gave up." The point is that whatever innings Miley would have pitched now will be pitched by
an asset they already have and have already committed to pay. Let's say Miley would have pitched 175 innings. The Sox were in position that they didn't need to go out on the market and pay anyone anything to fill up those 175 innings. They will be pitched now by players already under control who otherwise wouldn't have been playing those innings. Let's say maybe Kelly, or a combination of Kelly, Wright, Owens, whatever. Those guys also will accumulate WAR in those same 175 innings that they otherwise wouldn't have. And, indeed, WAR is really not all the difficult to accumulate for starting pitchers. A replacement pitcher, is, by definition, not very good. He's someone who costs no significant assets to acquire. For pitchers, he has a win percentage of about .380. A team of replacement players wins like 46 games. It changes year to year, but replacement FIP was something like 4.40 last year. For a pitcher (or group of starting pitchers) who pitch 175 innings, it doesn't take that much to start accumulating WAR. Even a pretty much repulsive 4.30 FIP means you're picking up runs over replacement, and the more innings you pitch the more runs (wins) that gives you. That's why a guy like Aaron Harang can put up a 4.83 WHIP (4.89 ERA, 1.39 WHIP) and still find his way to .8 fWAR -- it's because he pitched 172 innings and because the mythical replacement pitchers sucks even worse than that. So, if you want to talk about what we're losing in giving up Miley, it's the delta between the wins he would have given us, and the wins that his replacement, which we already have and who would be on the bench otherwise, is going to give us. That should be a much smaller number, unless you believe Kelly will never be better than replacement level (or, if he is, that the Sox won't find someone better in the system to pitch all or part of those 175 innings). You have to do the same exercise with Smith in reverse -- ask what he gives us over an existing asset that would pitch those 50 to 70 innings. But that's the resources point. The delta there is much likely to be greater, because it was an area of relatively greater need.
Edit: Sorry, I was working on that post off and on over some time, and so didn't notice buzzkill had made the same point about existing staff being capable of taking over Miley's innings at greater than replacement level value.