First things first: As I’ve been writing since last fall, there is no way the Mets can justify not spending significantly on free agents this offseason in this win-now window of theirs that is still open if they ever get lucky with injuries. And if their offseason haul turns out to be nothing more than Anthony Swarzak and, say, Adam Lind, in addition to re-signing Jose Reyes to play second base, Sandy Alderson is going to be pelted with more payroll questions, no matter how testy he gets on the subject. Maybe owners Jeff and Fred Wilpon will react to the growing criticism of their intention to lower that payroll, as they have in the past, and realize what a mistake it would be not to spend after they had some $60 million in expiring contracts — more if you add in the savings of the salary-dump trades of last summer and insurance money on David Wright. The slow-moving free-agent market is still so stocked with players, as all teams are waiting for prices to come down, that it’s too early to pass definitive judgment. In the meantime, it’s worth looking at the root cause for the Mets’ predicament: They’re in a position where they need to spend because their farm system is so weak at the upper levels, offering little in the way of major-league ready talent or prospects they can trade. Alderson has admitted as much, and there’s no mystery to it: His drafts, going back to 2011, his first season on the job, have produced precious few impact players. For the moment, in fact, Michael Conforto is the only star-type player to have emerged from the Alderson drafts. Other than Michael Fulmer, that is, and the Mets dealt him to the Tigers for Yoenis Cespedes in 2015. But let’s get that narrative, which I’ve read and heard plenty this offseason, out of the way right now: Yes, the Mets gave up several minor leaguers in trades to boost their playoff seasons of 2015 and ’16, but, Fulmer aside, those deals aren’t a factor in explaining their weak farm system.