Archie Manning, in his 12th year as quarterback for the New Orleans Saints, was traded to Houston yesterday for offensive tackle Leon Gray, who had been a holdout until this deal.

"It's a tough decision," said Saints Coach Bum Phillips, "an especially tough decision when you're talking about a guy like Archie who's been here so long." He said Manning and Gray would report to their new clubs immediately.

Gray flew from Boston to Houston yesterday and perfunctorily signed an Oilers contract that allowed the club to trade him. He then flew to New Orleans.

A shaken Manning said he had learned of the trade only a couple of hours before the announcement. "It's kind of tough," Manning said. "I've been here so long. I'm just going to look at it as something good and go over there and make a fresh start. It's the only thing I know to do."

Manning had lost his job as New Orleans' starting quarterback to Ken Stabler . . .

The managing general partner of the Seattle Seahawks says there's no truth to rumors that Coach Jack Patera will be fired as early as next week. Elmer Nordstrom also denied that Seahawks General Manager John Thompson's job is in jeopardy in the wake of the team's two losing seasons and a 21-7 defeat by Cleveland in the season-opener Sunday.

"We'd still like to have a winning football team," Nordstrom said. "So Jack's tenure is based a lot on having a successful season. And I think all coaches understand that, don't they?" . . .

The United States Football League has ruled that Willie Young's contract with the Chicago Blitz is valid. Young, 26, the father of five children, played last season at the University of Illinois after being recruited out of the Army. He was ruled academically ineligible at Illinois but said, regardless, he was not financially able to remain in school. "He did have three more years of eligibility remaining, never planning to get back to school," Blitz spokesman Kay Schultz said. "He wanted to get on with his life."