The disclosure Friday night that at least two of the "Heavyweight Championship of Tennis" challenge matches promoted by Bill Riordan of Salisbury, Md., and nationally televised by CBS-TV did not have "winner-take-all" purses as advertised is not the only case of the tennis public being deceived.

Financially, the last two Riordan challenge matches - Jimmy Connors vs. Manuel Orantes at Las Vegas on Feb. 28, 1976, and Connors vs. Illie Nastase at Dorado Beach, P.R. on March 6, 1977 - apparently were structured similar to boxing title fights.

Connors, as the defending champion, was guaranteed $500,000 or 50 per cent of the net proceeds, whichever was greater, win or lose.

The challenger was guaranteed a lesser fee or percentage. In no sense were the matches "winner-take-all," as portrayed by promoters and TV commentators, and reported by the media.

There are other cases of the public being misled as to how much money tennis pros are competing for in a given match:

The purse for the 64-man Alan King Tennis Classic, played last week at Caesars Palace in Las Vegas and nationally televised by ABC-TV, was billed at $250,000, but only $200,000 was distributed as prize money, sources told The Washington Post.

The other $50,000 (20 per cent of the announced prize money) went to the Association of Tennis Professionals (ATP), the players' union, as a promotional fee, the sources said.

Connors, who won the tournament, reportedly balked at the withholding of $10,000 from his first prize check, announced at $50,000, because he is not a member of ATP.

Many tournaments in the past have distributed less than their announced prize money because their contributions to the Grand Prix bonus pool - a fund distributed to the top finishers in cumulative point standings at the end of the season - were taken out of the prize money. This practice generally has been abandoned, however.

When Bjorn Borg signed with the Cleveland-Pittsburgh Nets of World Team Tennis in February, it was announced that he had a three-year contract calling for $1.5 million. The contract is actually for only one year, with options to renew, and the salary figure was inflated, sources close to Borg say.

A spokesman for International Management Group, which represents Borg, acknowledged that the Wimbledon champion is committed to WTT for only one season and likely will not renew his contract in 1978. Asked why a three-year pact had been announced, the IMG man said, "You know, it's the usual schmalz. It's done all the time."

Apparently he is right. Some promoters seem to feel that misleading the public to ballyhoo the event is their prerogative.

Claims that a $250,000 purse, winner-take-all, were at stake when Connors defeated Orantes at Caesars Palace and Nastase at the Cerromar Beach Hotel in the last two "Heavyweight Championship" matches were apparently nothing more than a publicity hype by the promoters and CBS-TV, which put up most of the money.

Connors defeated Rod Laver in the first "Heavyweight Championship," billed as $100,000 winner-take-all, on Feb 2, 1975. He defeated John Newcombe in a similar match, supposedly for a $250,000 winner-take-all purse, on April 26, 1975. Both matches were played at Caesars Palace.

Details of the financial arrangements of those matches were not immediately known, Riordan was unavailable and a spokesman for Caesars Palace declined comment.

Terms and conditions of Connors' participation in the Orantes match were detailed in a letter agreement, dated Aug. 15, 1975, signed by Connors and Riordan.

"In consideration of my commitment to participate in the 'Heavyweight Championship of Tennis' challenge matches. I will receive $500,000 or 50 per cent of the 'net proceeds' of the 1976 event, whichever is greater, win or lose," Connors' letter to Riordan says.

The letter goes on to define gross and net proceeds and says gross proceeds of the challenge matches "are anticipated to be in excess of $1 million based on the present commitments of CBS and Caesars Palace to provide $650,000 and $300,000, respectively, for each event of the 'Heavyweight Championship of Tennis.'

"I agree to defend my title in a subsequent event . . . on the identical financial terms set forth above," Connors' letter continues. "If I do not successfully retain my title in the 1976 event, I understand that I will receive 30 per cent of the 'net proceeds' (as defined above) for participating as a challenger in a subsequent event . . ."

A copy of the agreement was obtained by The Washington Post.

The document was attached as an appendix to a claim filed by Connors against Riordan in U.S. District Court, New York, in which Connors says he received $500,000 for the Orantes match but seeks a complete accounting to determine if he is entitled to additional payments.

Connors' action is a counterclaim to a suit filed by Riordan, seeking commissions he says are owed him for business deals he made when he was Connors' manager.

The New York Times reported Saturday that Connors was guaranteed $500,000 and Nastase $150,000 for their March 6 match in Puerto Rico, but quoted Riordan as saying the Orantes match had a $250,000 winner-take-all purse, plus ancillary revenues for both participants.

It was widely reported at the time of the challenge matches that both participants received considerable ancillary revenues, but these were believed to be above and beyond the announced $250,000 prize for the winner.

The "winner-take-all" challenge series staged by World Championship Tennis of Dallas the last two years lived up to the advertised format, according to informed sources.

Nastase reportedly received $100,000 and Connors nothing for the April 10 final of the WCT Challenge Cup at Caesars Palace won by Nastase.

John Alexander of Australia said that it cost him more than $4,000 in expenses to participate in the 1976 WCT Challenge Cup, a series of head-to-head challenge matches among eight top players, that was played over a four-month period last spring in Hawaii.

Alexander lost all three of his matches and said he received no prize money. He said all matches were indeed winner-take-all, as announced.