NBA

Blown lead shows you can’t trust Knicks yet

The Knicks probably haven’t played a better half all season than they did during the first half last night against the Grizzlies. Playing tough aggressive defense and displaying good ball movement on offense, the Knicks built a 30-point lead before settling for a 69-41 advantage at the break.

Blowout? Not so fast.

As good as the Knicks performed in the first half, they played almost as poorly in the second half, but eventually outlasted the Grizzlies, 108-101, last night at the Garden.

Despite the hot-and-cold outing, the Knicks claimed their sixth straight win, which is all that really matters. Even coach Mike Woodson was willing to overlook the second-half collapse.

“The game happens in spurts,” he said. “The beauty about it is our guys didn’t crack and found a way to win.”

Perhaps we shouldn’t blame the Knicks for getting bored in their own game and losing focus. It was the second of two back-to-back wins during the streak. That says something for perseverance.

Yet, the meltdown raises questions about how much stock we can put in this winning streak. Six wins is six wins and Woodson isn’t about to give any of them back.

“I was pleased with the way we played,” he insisted. But the victories have come against less-than-imposing opposition — the Knicks have beaten the Jazz, the Magic, the Raptors twice, the slumping Celtics and now the Grizzlies.

The Knicks would like to think they are back to a winning formula that can be dependable. Before the game they talked about being committed to staying atop the Atlantic Division.

“We’re playing for something,” Woodson said. “We’re trying to stay at the top of our division. Guys have been committed. They’ve been committed all year.”

But it wasn’t that long ago when the Knicks’ lead seemed in jeopardy after they lost four straight and five of six games. But after six straight wins, the Knicks believe they have regained their swagger and their confidence. Perhaps more importantly they’ve found a rhythm to how they want to play on offense and especially on defense.

“I think we’re back to that mode of knowing each other, feeling comfortable in terms of a [defensive] rotation, and we’re getting a lot of deflections and steals,” Woodson said. “That helps when you’re trying to build a defense and stay consistent about how you play defense.”

It was hard to argue against any of that during the first half last night, when the Knicks operated in unison on defense and they moved the ball with precision on offense. It looked like an easy night. Then came the second half when Memphis slowly whittled away the lead and the Knicks looked more like the team that endured the recent losing streak.

The Grizzlies got to within four points at 103-99 with 33.3 seconds to play. But the Knicks, with former greats like Patrick Ewing and Dr. Dick Barnett in attendance, used free throws by Raymond Felton and J.R. Smith to secure the win.

Woodson has tweaked the starting lineup by inserting Pablo Prigioni at guard ahead of Jason Kidd and adding Kenyon Martin to replace Tyson Chandler. Both have provided added energy on defense. They did so again last night until the second half, when everyone seemed to be wearing work boots. Truth is, you can’t take anything about the Knicks for granted these days — winning streaks or 30-point leads.

With Chandler out for the short-term and Amar’e Stoudemire out probably until the playoffs, the Knicks will have to make adjustments when they return. That could upset the rhythm they insist they currently enjoy.

Still, it’s as fragile as a golfer’s swing. Last night proved their rhythm on a basketball court can be lost in an instant.

george.willis@nypost.com