Even after more than a decade without a champion in the four major sports, nobody outside of New York ever wants to hear how tough the Big Apple’s sports fans have it.

But really, it’s not easy being a Knicks fan.

Even the wins — such as Sunday night’s season-saving 106-100 victory over the Indiana Pacers in Game 3 of the Eastern Conference finals — are agonizing, stomach-churning rides that remind fans of all that could and has gone wrong while offering just enough hints that perhaps this season will be the one in which the emotional investment finally pays off.

For most of Sunday night, the Knicks appeared likely to lose convincingly and fall down three games to none, a hole out of which no NBA team has ever emerged.

The Pacers raced out to a 20-point first-half lead that called into question whether this was the ceiling for these Knicks, who won 51 regular-season games while leaning heavily on a starting five that averaged 99.6 points per contest.

But depth becomes pivotal during a two-month postseason in which the champions are also almost always led by at least one generational superstar.

Head coach Tom Thibodeau, who is frequently criticized for his bench usage (or lack thereof), swapped out Josh Hart for Mitchell Robinson on Sunday night. Yet Hart and fellow reserves Miles McBride, Deion Wright and Landry Shamet combined for just seven points in the first half.

The bigger concern was Karl-Anthony Towns, who was acquired from the Minnesota Timberwolves in a blockbuster trade late last summer with hopes he could become the Knicks’ superstar. Towns was a double-double machine in the regular season, but he scored two points in fewer than six minutes in the fourth quarter of Friday’s 114-109 loss and remained almost invisible in the first half Sunday, when he had four points on 2-of-7 shooting.

At halftime, as footage of an errant Towns 35-footer aired, TNT’s Shaquille O’Neal declared, “… we’d be fighting in the locker room right now” if he had a teammate hoisting shots like that in a playoff game.

But Towns helped complete the Knicks’ third borderline miraculous comeback of the playoffs by collecting 20 points and eight rebounds in the fourth quarter. Towns scored all his points in the first seven minutes of the fourth before the usual suspects, Hart and Jalen Brunson, produced the final eight points as the Knicks earned their first postseason win in 10 tries at Gainbridge Fieldhouse.

The roller-coaster ride will continue in Tuesday’s Game 4, along with the questions that persist around and about the Knicks.

Are the Knicks the uniquely New York-tough bunch that has won seven of nine playoff games by single digits while becoming the first NBA team ever to win three postseason games in which it trailed by at least 20 points? Are they a real candidate to finally end a 51-year championship drought by becoming the first sum-is-greater-than-the-parts team to win it all since the 2004 Detroit Pistons?

Or are they fundamentally flawed and as prone to stunning collapses as they are to inspiring comebacks? Let’s not forget — not that Knicks fans could do so even with a collective lobotomy — how the series began last Wednesday, when the Knicks blew a 14-point lead in the final 2:40 of regulation in a 138-135 overtime loss.

With the Knicks still facing an uphill climb against the younger and deeper Pacers, that’ll probably be the rueful what-if that haunts Knicks fans all summer.

But after Sunday night, what if it’s not?