Coked-up Knicks players fixed games as a favor to their drug dealer — who bet big bucks against the anemic New York squad, FBI informants claimed during the 1981-82 season.

The feds probed whether three Knicks, reportedly “heavy users of cocaine,” and their supplier, “one of the largest dealers on the East Coast,” shaved points, according to FBI documents cited in Brian Tuohy’s book, “Larceny Games: Sports Gambling, Game Fixing and the FBI.”

The dealer was a degenerate gambler who usually bet $300 a game, informants told investigators, but in January 1982 he began laying $10,000 wagers on Knicks’ opponents — and winning them.

By March 25, the coke dealer had won six of his seven five-figure bets against the Knicks — while continuing to make his normal $300 wagers on other NBA games.

“Over . . . the last two months, all three [players] have given . . . tips on when to bet the Knicks to lose. This has occurred seven times and six of the tips were good,” according to FBI files citing two unnamed “sources.”

At the same time, FBI moles began to suspect the Knick trio were “betting against themselves.”

In November, an informant told the feds one of the schemers owed a “large . . . gambling debt” to a Luchese crime-family bookie.

“So many people say it’s impossible to fix a game because guys are paid so much money,” Tuohy told The Post. “But you can see how easily they can get hooked on some drug, be gambling themselves and get in deep with a bookie.”

A point-shaving hoopster could tank his performance to make the final score closer than it should be, helping those who bet the underdog. Or, a crooked player could make mistakes to inflate the margin of defeat, aiding a favorite-bettor.

Initially, an FBI source didn’t believe players were shaving points, but merely “extending a courtesy to their cocaine dealer, regarding inside player information,” the documents read.

But that opinion changed by late March as the dealer’s windfall grew. “Source now believes that the players are actively engaging in ‘shaving points’ and possibly even betting against themselves,” the feds state.

“Source observed heavy betting by [redacted] toward the latter part of the season . . . on the Knicks to lose certain games. In each case, the Knicks did lose, or failed to cover the point spread,” the FBI file reads.

The names of the players and the dealer are redacted in the FBI documents, which The Post authenticated with the federal agency.

The Knicks were owned at the time by Gulf+Western, and led by guard Micheal Ray Richardson, who averaged almost 18 points per game despite a rumored cocaine addiction.

Richardson famously said, “The ship be sinking,” as the team fell to 33-49, finishing last in the Atlantic Division. He was banned for life from the NBA in 1986 for violating the NBA’s drug policy three times.

“Hell no!” Richardson, 58 and living in Texas, told The Post when asked about the point-shaving allegations. “We never did anything like that.”

The Knicks declined comment.

The team was coached by the late Red Holzman.

Alex Bradley, a rookie on the squad, said players phoned it in — but not to bookies.

“At times the coach was a little lax, and he didn’t put enough pressure on those guys [to play harder],” said Bradley, now a security guard in Wilmington, Del. “At certain times, when we needed to turn it up, it just wasn’t there.”

The feds’ probe stretched into 1986, and widened to the coke dealer conspiring with “various professional basketball teams to shave points.”

But without any physical evidence — and no confessions — the Knicks case crumpled. An FBI spokeswoman said the case was closed, without any arrests, in 1986.

Around the same time as the Knicks probe, the FBI and the NBA, along with other sports leagues, began the Sports Presentation Program, sending agents to teams to discuss the dangers of sports gambling and bribery.

“It was no coincidence,” Tuohy said.

Additional reporting by David K. Li