A FEW MONTHS ago, I outlined what I thought was a sensible relationship between a professional athlete and his attorney and/or agent for contract negotiations. The bond that cements this partnership is mutual trust. Both the star and his representative stand to lose a lot of credibility if the star fails to keep his word.

His word is spelled out in the contract he signs. As salaries escalate, sports lawyers are having to write agreements that are more and more complicated. Nolan Ryan's total compensaton from the Houston Astros, for example, may differ depending on the kinds of years he'll have while playing.

At times in recent years, incentive clauses in baseball players contracts have not been permitted. In those years, if a players received a bonus after having a good season, it was thought of as largesse on the part of the club owner.

Were some of the athletes of the '40s, '50s, and '60s underpaid? Undoubtedly. But once you affixed your name to the contract, you were expected to keep your word.

Bearing this in mind I bring up the cases of Marques Johnson, "super John" Williamson and Thomas (Hollywood) Henderson.

Johnson interests me for three reasons: he used to be represented by my attorney, Donald Dell; he attended college at my alma Mater, UCLA, and I was baffled by his reasons for switching lawyers.

He had the best publicly reported multiyear rookie contract in the history of the NBA. He told me he was very pleased with his contract and Donald Dell and that he was confident he would do well in the NBA.

He proceeded to live up to his expectations in his rookie years with Milwaukee, whereupon he decided he wasn't compensated enough. He asked Dell to renegotiate his contract. Dell refused. Johnson then switched lawyers.

Quite a few pro athletes these days erroneously equate their high salaries with a unilateral right to renegotiate their contracts whenever they feel their compensation is not commensurate with their talents.

Because I live in New York City, I naturally follow the New York Knicks and the New Jersey Nets.Which means I follow Williamson, who plays for the Nets. Supe, as he is sometimes labeled. is extremely talented.

He was also ill-advised in his recent decision to miss practice. He supposedly did this because in basketball one player can affect a team's perfoamance and attendance. The theory was that the Nets would miss him so much that they would renogotiate his contract to get him to play again.

Perhaps he'd do well to reflect on the experiences of Eric Money, who now plays for the Detroit Pistons at a reported $50,000 a year. Before he started missing planes and practices, Money was making $115,000 to $130,000 with the Nets.

Williamson makes between $175,000 and $190,000 a year. That's not enough, he says. Meanwhile, he is not even starting.

But the issue is what he signed his name to and what the grounds are for renegotiation.

And now there is Henderson, the retired Dallas Cowboy. After he performed so well in the past he added the nickname Hollywood to match his new image and possibly to build up his reputation. Nothing wrong with that -- until he asked the Cowboys front office to renegotiate his contract.

Knowing the Cowboys' penchant for discipline, their answer to his demand was as predictable as whether Tom Landry would smile on the sidelines during Monday night football. In their own way, the Cowboys told Henderson to play out his contract as signed or find another job.

When Bum Phillips, coach of the Houston Oilers, was asked whether he would pick up Henderson, he said, "It seems to me that if a fella can't get along in Dallas he may not get along in Houston either."

Is there collusion among the front offices in pro sports to blackball troublemakers? Maybe. But meanwhile Johnson, Williamson and Henderson are making it tougher for the draft choices in the '80s.

If thsi whimsical breaking of contracts by either wide continues, three nasty possibilities may surface: 1) more collusion, either overt or covert, on the part of the owners to blackball contract breakers, 2) more short-term contracts to make it easier to dump a player, thereby lessening his security, and 3) more government regulation of pro sports because of the use of prime public property by sports teams.

We players can go a long way toward forestalling these alternatives if, when we sign our contracts, we keep our word. For that, we need to hire honest agents to negotiate for use our long-term interests at heart. I fully expect more team owners and general managers to follow the lead of the Cowboy front office if the pro athletes don't honor their written commitments.