Players have had this much of an impact. Coaches have made huge improvements and changed attitudes. But never a GM. Until now.

In Marv Albert’s years of following the NBA, no GM ever has transformed a team as quickly as Isiah Thomas has remade the Knicks.

“I have never seen a general manager have this sort of immediate impact,” Albert said of Thomas, who replaced Scott Layden on Dec. 22 and quickly began turning over the roster.

“Even before he made the [Stephon] Marbury trade. Suddenly, there was an edge to the team. There was a willingness to play defense. It just changed. I have never seen anybody have that type of difference who is a GM.”

Because of Thomas, when LeBron James arrives at the Garden on Sunday, New York hoop fans won’t be rushing to MSG just to see the 19-year-old wonder kid. They’ll be there to check out their rejuvenated Knicks.

“It is kind of amazing what has been done,” Albert said. “It is a renaissance from a team that was just sort of playing it out to a team gunning for playoff position. They became accountable. I just didn’t think they were accountable before for whatever reason. They just weren’t.”

Watch how aggressively the Knicks will defend against James.

“Right now, there is a buzz anyway,” Albert said. “There will be a lot of excitement for a guy who I think has surprised everyone that he has been able to make this adjustment [from high school] so quickly. I think he is the type of kid who will come back every season with more because of his work ethic and the way he handles things. I don’t think anyone thought he would be this good this quickly.”

Albert was talking about James. He could just as well have been talking about Thomas.