For years it has seemed, at least in the view of New Yorkers, that the opportunity to play in the greatest city in the world — and in Madison Square Garden, the world’s most famous arena — would be a powerful lure for the N.B.A.’s most talented players to sign with the Knicks.

But, then again, these are the Knicks, who have not won a championship since 1973 or a conference title in two decades and who are now better known as a hapless organization with a long streak of bad choices and bad luck.

So when a staggering jolt came Sunday as two of the league’s superstars, Kevin Durant and Kyrie Irving, not only ignored the Knicks but opted to join the Nets in Brooklyn, it made for a powerful reckoning: New York is no doubt a draw, but something is wildly wrong with the Knicks.

“That’s the punch to the gut,” said Jeff Van Gundy, a television commentator and a former coach of the Knicks and the Houston Rockets. “If you would have told me that two free-agent stars were going to choose New York and both would choose the Nets over the Knicks, I never would have believed it.”