Jason Varitek's not going to play any more.
Nobody seems to know how to measure a catcher's defensive value.
How are those two statements related?
Here's Over the Monster's (and Baseball Nation's) Marc Normandin on Varitek and the recent advances in measuring catcher defense, with most of the math stripped out (by me):
Jason Varitek has long been lauded for his ability to handle a pitching staff and call a game. This praise has all been anecdotal, as catcher defense as most of us know it is still very simple when represented statistically. Varitek doesn't get any credit for his perceived ability to call a game when defensive statistics focus on his ability to throw out runners and catch pop ups behind the plate.
Since he has struggled over the years throwing out runners, and has been nowhere near as effective at the plate in his later years, the whole pitching staff handling theme seemed more like a defensive reaction from his proponents to prop up Varitek's value and purpose, rather than a legitimate point in his favor. When you can't measure something, you often take it for granted as being unimportant. But that's not the case: it often just means we haven't figured out what it's worth yet.
It's a rough sketch, but whereas Varitek was considered worth -3 runs by FRAA from 2008-2011, when combined with Marchi's figures, he's worth nearly six wins in the same stretch. That would put Varitek's overall value at over eight WARP, rather than the 2.6 he posted over the last four years. He would be around six wins via Baseball-Reference, and nearly seven wins according to Fangraphs. That's a significant difference, and shows that Varitek was still productive, even at the end of his career.
There's a dissonance here, right? If Varitek's been worth 6-8 Wins Above Replacement over the last four seasons -- and that's while playing just semi-regularly -- why is everyone letting him retire? Shouldn't teams have been lined up outside his house all winter, begging to give him $6 million to play this year?
Well, of course most teams aren't yet buying into these cutting-edge catcher metrics. But the Red Sox must have their own. And yet Kelly Shoppach will be the backup catcher this season, while Jason Varitek goes off and does whatever ex-catchers do when nobody appreciates their veteran game-calling skills any more.
All of which is just an excuse for me to point out there's still a lot we don't know, but guys are working on it. And when the guys figure that out, there will be something else.