On a night Kristaps Porzingis fell back to Earth, the Knicks needed their big free-agent acquisition, Tim Hardaway Jr., to give them life.

Instead, Hardaway became a Boston bust to continue a disastrous start to his second stint as a Knick. In truth, almost every Knick who hit the hardwood Tuesday stunk out Beantown and afterward an exasperated Hardaway said the offense was disorganized and “lackadaisical.”

With the Celtics taking a 21-point lead just 15 minutes into the game, the Knicks were whipped up and down by Kyrie Irving’s depleted team in green, 110-89, at TD Garden. After an 0-5 preseason, the Knicks are winless in their first three regular-season games.

“We’re all out there just running like we don’t know what’s going on,’’ Hardaway said. “It can’t happen. It’s frustrating at the same time, but it’s still early in the season. We’ve just got to go to the drawing boards and get back to practice, just go out there knowing what we have to do offensively and defensively.”

Hardaway couldn’t throw the ball into Boston Harbor — a 2-for-11 outing that brought his three-game shooting ledger to an embarrassing 9-of-37. It’s a nightmare start after signing a whopping $71 million deal.

The facial expressions of Knicks president Steve Mills and general manager Scott Perry moments after the game spoke volumes. They looked ashen.

Hardaway’s defense also left much to be desired and the entire Knicks team was lethargic in getting back in transition defense.

Hardaway shot well — 50 percent — in the preseason, but now is facing a crisis. He acknowledged he tweaked his ankle in preseason, but wouldn’t use it as an excuse for his shooting woes.