Devils fans showed up in numbers to Madison Square Garden on Monday night to see it.

Their flourishing, Metropolitan-leading Devils marched into enemy territory, winners of 15 of their last 16 games, to take on the slipping Rangers for a power-struggle battle after years of simmering in their shadow. Their team did not disappoint, but the Rangers did as they allowed another multi-goal lead to vanish in an alarm-bell-sounding 5-3 loss — their third in a row.

The Rangers had won nine of their last 10 games against the Devils dating back to March 4, 2021, and had gone 14-6 since 2018-19. This was a Devils team that the Rangers finished 47 points ahead of last season, when they reached the Eastern Conference final while their counterparts across the Hudson watched from afar for a fourth straight year.

Two things are for certain after this game: The Devils are no joke and the Rangers are in a predicament.

The mistakes have been costly — exasperating even — given the fact that the Rangers aren’t getting the same otherworldly saves from Igor Shesterkin. There’s no question he is still at the heart of this team, but it is not to the degree that it was during his Vezina Trophy-winning season in 2021-22.

Fans in red even felt confident enough to taunt Shesterkin, echoing his name throughout the lower bowl as he gave up three goals on 15 shots at one point before ultimately allowing four on 37. The Devils’ signature ‘Woo’s!’, which multiply when a game is leaning heavily in their favor, seemed to mock the Rangers.

It’s also not just the Rangers’ turnovers, but how those mistakes always seem to end up in the back of the net one way or another.

The Rangers blew their second multi-goal lead in as many games, but it all went down in the opening 20 minutes instead of the final frame — as was the case in their third-period collapse against the Oilers on Saturday.

After Artemi Panarin snapped a 12-game streak without a goal less than a minute and a half into the game, Devils goalie Vitek Vanecek fumbled a Jacob Trouba shot and Mika Zibanejad jammed home the rebound to give the Rangers a 2-0 lead roughly three minutes after the initial puck dropped.

A two-goal deficit didn’t faze the Devils in the slightest. Their confidence with the puck never wavered, and the visitors finessed their way back into the game before the first period even ended.

Tomas Tatar finished a smart passing sequence on the rush, roofing a backhander over Shesterkin. A team that’s clicking as well as the Devils are right now is going to get those looks, but Trouba, the Rangers’ captain, served up their next goal after a tough giveaway at the top of the defensive zone.

Once the Devils stuffed the puck back into the Rangers’ zone, it popped out to Yegor Sharangovich in the slot for a turnaround shot at 13:25 of the first period. The Devils then doubled their score off goals from Jack Hughes and Michael McLeod in the second period without an answer from the Rangers.

It wasn’t until there was 6:42 left in regulation that Vincent Trocheck made it a one-goal game for the Rangers, who failed to capitalize any of their four man-advantage opportunities in the final 20 minutes. The Devils still closed them out, adding an empty-netter for good measure, despite getting outshot 17-5 in the final frame.

No matter if it was in the first, second or third periods, the Rangers haven’t always effectively preserved leads this season. Whether the Rangers are getting too comfortable or playing not to lose instead of to win, there is no will to protect the lead at times.

There was a shift that unfolded on the Garden ice Monday night. The Rangers were on the wrong end of it.