A paunchy Kenny Stabler emerged from a five-week retirement yesterday and said the injury to Houston Oiler's quarterback Gifford Nielsen brought him back for his 12th NFL season. "I made up my mind a couple of days ago," Stabler said. "I'm not sure why. I think I unretired and retired several times. I think after Gifford got hurt I saw the Oilers needed me."

Neilsen was injured Saturday during a preseason game with Tampa Bay.

Stabler said his retirement was sincere and had nothing to do with contract negotiations. "When I retired I sincerely retired. That's a true story," he said."But I thought retirement was going to be easier than it was."

Stabler said he was overweight at 210 pounds. He said his only activity since December had been "hanging around down at the beach" in Gulf Shores, Ala. "I did very little (conditioning) because I retired. There was no reason to get in shape because I wasn't coming back," he said.

The Oilers lured the NFL all-time pass completion percentage leader back to the game with a two-year contract. The team would not disclose details but said the contract's terms were close to those Stabler played under in 1980, when he was paid an estimated $400,000.

Coach Ed Biles said it was conceivable Stabler could start the Oiler's season opener Sept. 6 against the Los Angeles Rams.

"He can pick the system up in a few days, but how he is physically is another question," Biles said.

The Denver Broncos waived Matt Robinson, trimming their quarterback contingent to three and their team roster to 49.

With Robinson gone, Jeff Knapple became the Broncos' No. 2 quarterback, behind veteran Craig Morton and ahead of rookie Mark Herrmann.

Coach Dan Reeves said the Broncos "hope we can bring Mark along slowly and give him experience so he can play. A lot depends on how Jeff does."

Robinson was the starter early last season, before Morton regained his job.

Defensive tackle Randy White, who threatened to sit out the season, signed a multiyear contract with the Dallas Cowboys that will make him the highest-paid lineman in the league, a club official said.

No terms were announced but he probably will make more than $200,-000 a year.

White is a seven-year veteran from Maryland.

All-pro defensive end Fred Dean of the San Diego Chargers said there is a "possibility" he may sit out the season because of a contract dispute.

The seven-year veteran, who missed the first two games in 1980 because he was unsatisfied with his contract, did not report to the Chargers' training camp this week.

Wide receiver John Jefferson has missed the entire preseason because of problems with his seven-year contract, which has four years to run.

Theo Bell has not reported back to the Pittsburgh Steelers' training camp and is threatening to sit out the season because of his contract.

The league gave the Steelers permission to carry Bell as a 51st player on the roster indefinitely until he surfaces, a team spokesman said. Dan Rooney, president of the Steelers, said Bell would be placed on the reserve list if he doesn't return. This would mean he cannot play this year.

Bobby Bryant, veteran cornerback with the Minnesota Vikings, has retired.

Bryant, 37, had been with the Vikings since they drafted him on the seventh round out of South Carolina in 1967. He spent his first season on injured reserve.

The Vikings also announced signing defensive back Walt Williams, cut last week by the Detroit Lions.

Middle linebacker Tom Cousineau of the Montreal Alouettes will miss the remainder of the Canadian Football League season because of calcium deposits on his left elbow, a team official said.

The former No. 1 draft pick of the Buffalo Bills of the NFL was told by doctors it would take at least a month to treat the elbow and as much as three months for rehabilitation.

The 6-foot-3, 227-pound Cousineau, a former all-America from Ohio State, started just three games for the slumping Alouettes, who have won one of seven games this season.