To echo a couple other posts, he was a very good, underappreciated player. Three days after Gil Hodges died, the Mets traded him in a 3-player package for Rusty Staub, and while Rusty was of course a fine player, Singleton was at least his equal if not better over the next few seasons (148 OPS+ in 1973) as well as 3 years younger. And then the Expos traded him (along with Mike Torrez) to Baltimore for a washed-up Dave McNally and Rich Coggins in an absolute steal of a deal for the O's.
As a broadcaster, I appreciated him for making the YES booth tolerable; always good when he was there and Kay wasn't.