To me, the most useful part of stats and WAR is the area that has been discussed many times before. Most of us watch only the Sox game with maybe a few others here and there plus playoff games that we are not a part of.
We may not even see some players for one inning on TV. Others we may see for 3 games on TV. Others six. Some we see live 1-2 games and on TV another 15-16 times, if they happen to play in the AL east. We see Sox players 100-162 games a year.
It's nearly impossible, with any degree of certainty, to know or claim our guy is better than theirs. I know I'd be more than 17% off, if I had to just use my own observations to rank and value players with a single number by myself.
We all look at a player we've never seen, who is hitting .320 45 120, and we know he's a damn good player. How do we know that? We rely on stats and data. When it comes to defense, it gets a little more hazy, because FLG% is a horrible measure for defensive greatness or ineptitude. While I realize UZR/150 is flawed, it is light years better than my own observations and fldg% by themselves. I do see other great plays by CF'ers in Sox games. I see some on Sports Center. I know other great defenders are out there. How good are they? How do they compare to JBJ? Nobody know for sure. Even if a single person watched every play by CF'ers one very team over a given year, there would still be bias.
For arguments sake, lets say there was a metric that was 100% accurate for evaluating a CF'er's defense. Then, we ask each of us to numerically place a value on each MLB CF'er. How far off do you think we'd be? How would I ever know how to value the Padre CF'er, of the Diamondback CF'er, and on and on...? I'd be 80% off on some, for sure. I'd be much more than 17% on just about everyone, except maybe a few Sox players and AL east players, for sure.
I try not use UZR/150 like the Bible, but I know I have come across like that at times. I do trust it more than my own observations, even if I think JBJ might be slighted by it.
I'm happy to know he is a top 5-10 defensive CF'er and know his defense brings so much value to the team that his offense is not a concern to me. I'm glad UZR/150 and WAR back up my belief by always rating him a plus. While I don't need metrics to tell me JBJ is a big plus, I do use it to know about other players with a certain degree of confidence.
I guess some of us have more "confidence" than others, and I understand why some feel slighted when WAR and UZR are continuously thrown in their faces, but I have to say that I probably sometimes feel the same way when someone who obviously does not watch every CF play by every player in MLB can claim that JBJ is the best defensive CF'er in MLB in a way that sounds like he is so sure of it.
Maybe JBJ is the best defensive Sox CF'er in each of our own generation. That claim makes more sense, because it may be likely we've seen close to every play made by a Sox CF'er in decades, but I think it is more folly to claim, by observation only, that he is the best CF'er in MLB today than to use UZR/150 to claim he is the 5th best defensive CF'er. Neither method is perfect, but it seems clear to me, one is better than the other.