Reposting from another forum on the off season.
This morning Dan Shaughnessy, whom I usually respect (partly because he answers emails), argues that Mookie Betts isn't any better than Fred Lynn or Nomar Garciaparra and that he should be traded, as they were when they were about his age. He is totally, completely, demonstrably, absolutely wrong.
It's interesting that Shaughnessy, to make his case, relies almost entirely on traditional statistics. I'm going to be using my own version of WAA (not WAR), which I developed for my book Baseball Greatness, in this post, but any park- and era-adjusted measurement, I am confident, would show the same picture.
A very quick intro here: WAA as I figure it usually is about 2 less than the corresponding WAR. The key threshold that I used in the book is 4 WAA in a year, which is what I call a superstar season. Historically, if you want to reach postseason (and certainly if you want to win more than 95 games) you need at least one player that good. They are rare, and getting rarer.
Here are Fred Lynn's WAA by my method in his years with the Red Sox:
1975 3.9
1976 1.2
1977 0
1978 2.8
1979 6.2
1980 3.2
There are two reasons why some of these figures (especially 1975) are lower than you might think. One is that Fenway gave hitters a much bigger advantage then than it does now. The second is that Michael Humphreys' DRA, incomparably the most accurate historical measurement of fielding, shows that although Lynn could make spectacular catches, he was not on the whole an above average centerfielder. He wasn't bad but he was not gold glove worthy.
Now let's look at Nomar Garciaparra with the Red Sox:
1997 2.1
1998 3.0
1999 4.1
2000 4.3
2001 0.2
2002 3.5
2003 2.4
Nomar, surprisingly, was a more consistent performer than Lynn, although his peak was not as high. After leaving the Red Sox, by the way, Nomar was never better than an average player.
And now, Mookie Betts.
2015 1.7
2016 6.0
2017 3.9
2018 8.1
2019 5.3
Now, if you can look at those figures and tell me that Betts isn't any better than Lynn or Nomar--good luck to you. The 8.1 season two years ago, by the way, ties with Mike Trout (also in 2018) for the best season by any player in the Millennial generation. Trout at the rate he is going will wind up in the top 10-15 players of all time. He has beaten 6 WAA in all but one of his first 8 seasons (and in that one season he missed nearly 1/3 of the year.) I think the only player who has ever had a first 8 seasons that good is Ted Williams. But beyond Trout, Betts is clearly the best player born in the early 1990s. One reason Betts does so well, by the way, is that unlike Lynn, he truly is an outstanding outfielder. (Nomar was an excellent shortstop in two of his early seasons; then he fell to around average.)
Betts's baseball age last year was 26. Here are Carl Yastrzemski's figures through age 26:
1961 -2.4
1962 3.5
1963 5.3
1964 2.6
1965 3.2
1966 5.0
Yaz got the majors earlier than Betts did, started more slowly, and wasn't as consistent in these years as Betts has been. And Yaz proceeded to have his greatest two seasons, 10 and 9.3 WAA, in 1967 and 1968, and he had 7.9 in 1970. Yaz is a much better comp to Betts than Lynn or Nomar.
There is another reason why the Red Sox should give Betts everything he wants to say in Boston. They can very easily improve their roster by switching him to center field. Jackie Bradley Jr. has been about -1 WAA for the last two years and shows no signs of ever being any better than that. The Red Sox should be able to find a good-hitting rightfielder somewhere, and if he earned 2 WAA and they switched Betts to center, then bingo, that's 3 more wins right there.
Based on run differential, the Red Sox are starting 2020 12 games behind the Yankees--and the Yankees had so many injuries that they could easily improve next year. Making up that deficit will be very difficult even with Betts. Without him I see no hope.