The last time the Yankees went this bad this late in a season, Derek Jeter was in his prime and his team was dynastic.

The 2000 Yankees won their 143rd game of the season to take a nine-game lead over the second-place Red Sox. They then lost 15 of their final 18. That doesn’t really represent the plummet. They had a seven-game losing streak — just as they carried into Saturday’s game against the Mets — and they lost eight of those final 18 by eight or more runs and six by 10 or more runs.

That team, like this one, thought it had solved so many of its ills with in-season acquisitions, notably David Justice and Denny Neagle. But Neagle was Joey Gallo-esque, unable to handle New York. They were beat up physically, couldn’t hit (.240 with a .671 OPS after .282/.820 before that) and couldn’t pitch (8.10 ERA after 4.36).

They held on to win the AL East by 2 ¹/₂ games because in the same period the Red Sox did not capitalize enough, going 10-9.

Those Yankees, of course, flipped an October switch and went on to win the most famous Subway Series vs. the Mets, capturing a third straight championship.

And that is where the comparison fades. Those Yankees were time-tested champions, full of not just talent, but fortitude. That group could look left or right and see a Jeter or Mariano Rivera, a Tino Martinez or Paul O’Neill, an Orlando Hernandez or Andy Pettitte. There was zero doubt about the group’s capabilities in that room. The trust in each other was part of their weaponry.

The 2021 Yankees have three World Series winners on the roster — Brett Gardner from the 2009 Yanks and Aroldis Chapman and Anthony Rizzo from the 2016 Cubs. For the most part, though, this team has a core that has been unable to navigate through the playoffs.

Now, they are vulnerable to not even making the postseason. We may look back and see that 13-game winning streak as the best and worst thing that happened to these Yankees. To construct it has seemed to take everything physically and emotionally out of this club as it won one closely contested game after another. Perhaps psychologically too — maybe the Yankees felt that they had guaranteed an invite to the tournament with two weeks of only winning.

But two weeks of almost only losing (2-11) followed in which the Yanks hit .214 and pitched to a 4.97 ERA. And what is the belief system in this club? There is no Rivera to provide a backbone, to deliver a sense that if the Yankees could just get the ball to him they would win. Chapman inspires no such confidence at a time when his importance has never been more exaggerated with Zack Britton out for the season and Jonathan Loaisiga out too.

After a few weeks of picking up their pace, the Yankees are back to lethargic, station-to-station offense in which they wait for homers and are persistently doused by double plays. They need a player or two to put the team on their backs. Aaron Judge and Giancarlo Stanton did that for a while. But they chilled and no one else warmed. The Yankees had five doubles in their first nine September games — or as many as Pete Alonso. They had one stolen base. They had nine double plays — third most in the majors.

They have compounded the problems of a depleted, exhausted bullpen by having a starter go fewer than five innings seven times in 11 games going into Saturday; and four of those times the starter did not even get through the fourth inning. That is worsened, of course, by the IL absences of Jameson Taillon and, especially, Gerrit Cole, who likely will return Tuesday.

It is all exacerbated by being in the midst of playing 20 straight days. There is no wall to hang onto to catch their breath. The Yankees are in the deep end — and in deeper trouble than seemed possible two weeks ago.

They were previously able to respond to a generally disappointing season by assembling that 13-game winning streak. Can they rebound again? The 2000 Yankees are proof that a quality team can flip a switch, even late on the baseball calendar. But that club was made up of champions.

What is this team made of?