Was Craig Kimbrel worth all those prospects?

Friday, the Mariners traded for a pretty good relief pitcher. Saturday, the Red Sox traded for a pretty great relief pitcher. Monday, the Rangers traded for a pretty good relief pitcher.

You might have noticed one different word in there. Or if you're a big HBO consumer, one of those things is not like the other. Which should be at least a small part of this conversation, I think...

Now, Joe did follow up with a note about Kimbrel's apparent decline; he was better in 2011 and '12 than he's been since.

Which is fair to mention! 

It's also fair to mention that Kimbrel was somewhat unlucky this year. He gave up six home runs, after averaging only three in the previous four seasons. There's just no reason to think those three "extra" big flies say something big about Kimbrel's abilities. So let's just look at xFIP -- fielding-independent pitching statistics, including a modifier for typical HR/FB ratio -- over the last two years and see where Kimbrel shows up...

Even looking at just the last two seasons, when he seems to have slipped some, Kimbrel ranks seventh among all MLB relievers with at least 100 innings.

He's also basically tied for fifth in fWAR, behind only Dellin "Ton o' Innings" Betances, Aroldis Chapman, Wade Davis, and Andrew Miller. Then you get a group that includes Kimbrel, Kenley Jansen, Cody Allen, Jake McGee, and a few others.

Roughly speaking, we're talking about Kimbrel as one of the 10 most effective relief pitchers in the majors over the last two seasons.

Is that worth all those prospects the Red Sox gave up to get him? Well, that sorta depends. It depends on how much you trust fWAR -- which suggests that even most Top 10 Firemen aren't worth a bushel of prospects. 

The good news is that Kimbrel's worth his salary. While his projected fWAR of roughly 2 per season isn't nearly Cy Young-worthy, 2 WAR is worth around $15 million, and Kimbrel's going to earn only $25.5 million over the next two seasons. And we're probably undervaluing WAR, considering the usual salary inflation.

Of course that's treating all the figures in a vacuum. Maybe such WAR/$$ equations don't really work for relief pitchers, since so many good relief pitchers can be found for relatively little money, either in trade or in your own farm system. These days, you can shake a tree and hard-throwing relief pitcher will fall out. For cheap.

Again, though, few of those hard-throwing relief pitchers would be quite as good as Craig Kimbrel. Does WAR miss something? A lot of baseball people would say it misses a lot! Monday, Jeff Sullivan came up with an interesting way of measuring what WAR misses with elite closers, and his conclusion was dramatic: An elite relief pitcher is worth an extra win-and-a-half, above what you'll see in the usual measures of value.

If true, things start to look quite a bit different. Now you're talking about Craig Kimbrel being a bargain for his salary over the next couple of years. 

Worth four prospects, though?

Well, this is one of those times when I will guess that if Dave Dombrowski could have gotten more for those four prospects -- only one of whom's a blue-chipper, by the way -- he would have. Not that Dombrowski's perfect. But most Directors of Baseball Things have a pretty good idea about value, and if he could have gotten a really good starting pitcher for the prospects, he probably would have.

No question, this was a fine move for the Padres. I didn't really understand the Kimbrel trade when A.J. Preller made it, but now it's looking perfectly fine. It will be a fine move for the Red Sox if Kimbrel arrests his (slight) decline and the blue-chipper, Manny Margot, doesn't turn into a big star soon. In that case, it would look like the Red Sox missed some things.

But we can't assume yet that anybody's missed anything. This looks to me like a couple of rational actors making reasonable choices in their particular circumstances.

Rob Neyer's been writing about baseball since Senior Griffey was a better Hall of Fame candidate than Junior. He's not too old for Twitter, though.