The NFL Players Association likely will file a grievance on behalf of quarterback Quincy Carter because of the conditions under which he was released by the Dallas Cowboys on Wednesday, a union source familiar with the case said Thursday.

It appears the Cowboys released Carter because of a violation of the NFL's substance abuse policy, and the terms of the collective bargaining agreement between the league and the union prohibit a team from releasing a player for a failed drug test, said the source, who spoke on the condition of anonymity because the grievance has not yet been filed. The collective bargaining agreement allows teams to release players for skill and performance reasons.

Cowboys officials have refused to specify the reasons for Carter's abrupt release. But Coach Bill Parcells and owner Jerry Jones talked Wednesday about their disappointment in having to make a move they said was necessary because of behavior that did not fit into a team concept, and an NFL source confirmed reports that Carter, 26, recently violated the substance abuse policy and was in the program because of a previous failed drug test.

Carter apparently is facing a fine equal to four regular season game checks for a second violation of the policy because a third violation of the drug policy results in a four-game suspension by the league, and a source said Carter was not facing a suspension. Parcells said Wednesday that, as far as he knew, Carter was eligible to sign with another team and play immediately.

It was unclear what remedy the union would seek in a grievance filed on Carter's behalf. It's unlikely the union would seek to have Carter put back on the roster of a team that doesn't want him, but it perhaps could seek financial remedies from an arbitrator. The union would have to prove Carter was released because of a failed drug test, but the source said that case could be made convincingly since Parcells had said shortly before Carter's release that Carter was the front-runner to remain the starter. Another potential hurdle for the union is the suggestion made by Jones on Wednesday that the Cowboys perhaps built protections for themselves into Carter's contract.

Players Association chief Gene Upshaw declined to comment on the details of the Carter case when reached by telephone Thursday but confirmed that a player cannot be released because of a failed drug test.

"I'll know more when I get to the Hall of Fame this weekend and talk to some people," Upshaw said. "I can't comment on a drug case."

Upshaw had expressed concern Wednesday about a report that Carter's recent failed test had been administered by the Cowboys. That would be a violation of the collective bargaining agreement, which stipulates that drug tests can be conducted only by the league.

But an NFL official said later Wednesday that the Cowboys do not conduct their own drug tests, and a source said the test Carter failed was administered by the league.

Parcells declined further comment on Carter here Thursday, as the Cowboys conducted a pair of training camp practices with Vinny Testaverde as their starting quarterback.

"I'm not going to talk about this subject any more," Parcells said. "It's not worth it. It doesn't really mean anything now. I have to go forward. That's what I'm doing. That's enough of me talking about that. I said what I had to say [Wednesday], and I really can't -- I don't want to, that's all."

Cowboys officials said Wednesday, and reiterated Thursday, that Jones and Parcells had been discussing Carter's status for some time, and the move was not necessarily related to a single incident. But a team spokesman said the club had no comment on whether Carter's release was related to a violation of the substance abuse policy and any possible action by the union stemming from that.

Quarterback Quincy Carter is no longer a part of the Cowboys after helping the team finish with a 10-6 record last season and a spot in the playoffs.