Joe Sheehan analyzes this question. I think it is premium content, but you don’t need to read the article.
Besides this ridiculous proposition:
Randolph isn’t a very good tactical manager, and it was his inability to manage a high-maintenance bullpen last year that cost the Mets games not in September, when no one was pitching well, but in May, June, and July, when some better choices in-game could have put the division away.
(It is ridiculous because, one, he or anyone else has no idea how good or bad Willie was at managing his bullpen, two, what does that even mean, three, he offers no evidence to support that claim, and I doubt there is any, and four, how many wins can a good or bad “managing” of a bullpen in “may, June, and July” be worth? .5 wins? 1 win? 1.5 wins? “Put the division away?” Please!)
Anyway, you don’t have to read the article, because I can tell you with some confidence, that despite my constant criticism of managers’ tactical strategies, we have no idea how much an over or under-achieving team is due to the manager. No idea. In case I am not being clear, I mean no idea. And I think we (analysts) should stop pretending that we do. Let’s leave that to the fans and the sports shock jocks.