NBA

DEEP-SIXED!

PHILADELPHIA – Finally fed up with his up-and-down Knicks, Isiah Thomas unleashed a caustic diatribe last night, saying the Knick fans want a playoff berth more than his squad.

Thomas questioned the club’s “desire” and mental toughness after the Knicks disgraced themselves here last night against the awful Sixers (18-36), getting clobbered 104-84 after blowing an 11-point first-quarter lead at Wachovia Center.

Thomas is usually upbeat even after defeats and often provides excuses for his team. But after losing in Philly twice this season – damaging their playoff hopes – he was disgusted. The Knicks, however, were banged-up. They played without David Lee for the first time this season and with an ailing Stephon Marbury, who played respectably but revealed he is limited by turf toe on the big toe of his right foot.

Thomas also benched a lethargic Steve Francis early in the second quarter for terrible defense and offense (he had an offensive foul and a bricked jumper). Francis played just 3:50. Thomas said emphatically, “THAT was a coach’s decision.”

“Our desire and our intensity just faded and went out the window,” Thomas said. “Right now we got to make a decision on how bad do we really want it. Our fans want it probably more than our players want it right now. There’s no explanation for what happened here tonight other than a matter of desire.

“You got to want it,” Thomas added. “You got to go get it. We didn’t want it bad enough and we didn’t go get it. That’s what’s missing with our team right now.”

Thomas said before the game he didn’t foresee making a trade today, but the team sure looked ready for an infusion after being outscored 35-16 in the game-turning second quarter and allowing Kyle Korver to go off for a career-high 31 points in 34 minutes off the bench.

Korver toasted Jamal Crawford and Francis, making 11 of 14 shots, including 6 of 7 3-pointers. Korver is the kind of perimeter marksman Thomas would likely want to add to this roster, but it’s unlikely the Knicks will make any moves at the trade deadline. Even though, they did talk to the Nets about Jason Kidd and Vince Carter, according to sources.

The Knicks (24-31) came out of the All-Star Break with a fine 100-94 victory over Orlando Tuesday before last night’s fiasco. “I definitely have to figure something out,” Thomas said. “We’re consistently inconsistent in winning one and losing one.

“It’s an area we’re hesitant to cross,” Thomas added. “It’s very disappointing.

“Mentally we got to get them to push though, it has nothing to do with the game of basketball,” Thomas added. “The mental approach to the game and crossing that barrier and accepting the challenge to become good, there’s hesitancy in our team right now. We don’t want to step across that line and become a good basketball team.”

Without Lee, who had the flu, and Quentin Richardson, who played just 23 minutes after reinjuring his bruised shoulder, the Knicks were pounded on the boards, 41-32.

The Sixers iced the game with 6:30 left when they converted what amounted to a five-point play. Joe Smith scored inside and was fouled. Though he missed the free throw, Samuel Dalembert hauled in the offensive rebound, kicked it out to Korver, who drained the trey as an 81-74 lead was jacked up to 86-74.

“When you look at that play, we’re missing that toughness to step across the line and chase it,” Thomas said.

With Jerome James making an impact as a starter and Eddy Curry (22 points), effective inside, the Knicks raced to an 8-0 lead and had an 18-7 advantage with 4:23 left in the first.

The Sixers shot 80 percent in the second quarter, making 12 of 15 shots. A rag-tag fivesome of rookie Mardy Collins, Crawford, a rejuvenated Renaldo Balkman, Curry and Jared Jeffries got the Knicks back into it with a late third-quarter flurry – a 16-2 run – but never got closer than five points. They were down five with the ball with 8:33 left when Crawford (3 of 12) bricked a 3-pointer and Korver soared in for a fast-break layup. The Knicks were never heard from again.

“When we came in, we knew how important this game was,” Marbury said. “To go up by (11), then go down by 19, it’s a drastic turnaround. When we get up, we got to sustain it.”

Curry said he did not agree with Thomas’ assessment the fans want it more than the team. “I can’t speak for everybody else but I know I want to make it bad,” Curry said of getting a playoff berth.

marc.berman@nypost.com