By MARC BERMAN

Disgraced referee Tim Donaghy, David Stern’s worst nightmare, filed a pre-sentencing letter in federal court Monday in which he crystallizes some of the NBA’s ethic problems.

Donaghy asserted not only do referee relationships with players effect the outcome of certain contests, but their relationships with coaches, too, have an effect.

Stern doesn’t want to hear it. The commissioner was so happy the Donaghy issue faded when the NBA season began last November. One reason is Donaghy’s sentencing kept getting delayed and delayed (it’s now set for mid-July, the offseason). Coaches and players were also banned from talking about Donaghy with the press.

My theory is Stern made such a giant issue of the Knicks’ sexual harassment case purposely to overshadow the referee-betting scandal. I believe that in my heart.

Stern indeed was more outraged at Isiah Thomas and James Dolan than when it was confirmed that some of Donaghy’s allegations were true, that referees broke their contract by betting in casinos in the offseason. Stern didn’t punish any of them.

Stern is expected at the Draft Lottery tonight – surely to deny the 1985 lottery was fixed. The commish will have to answer to Donaghy’s latest letter. You can bet he won’t admit to any overriding referee problem, sticking to the company line that Donaghy was an isolated incident. The truth would hurt too much.

Last night, Joel Litvin, one of the NBA’s VPs and top attorney, released a statement, trying to smear any validity to Donaghy’s claims as the league minimizes the perception the referees are biased.

Here’s Litvin’s take:

“The letter filed today on Mr. Donaghy’s behalf contains an assortment of lies, unfounded allegations, and facts that have been previously acknowledged, such as the fact that certain NBA referees engaged in casino gambling in violation of NBA rules. The letter is the desperate act of a convicted felon who is hoping to avoid prison time and the only thing it proves is that Mr. Donaghy is no more trustworthy today than he was when he was breaking the law by betting on NBA games.”

No, sounds like the NBA is “desperate” Donaghy goes away.