The worst trade the St. Louis Cardinals ever made was dealing coach Don Coryell to the San Diego Chargers for a No. 3 draft choice. The timing was just about as blameworthy.

Had he been seeking revenge, Coryell could not have picked a more opportune time to have his Chargers shut out defending conference champion Denver, 23-0, Sunday (the first shutout for the Broncos in 48 games).

At the same time, Bill Bidwill of the Cardinals became the target of the first known campaign to have an owner fired, after his team lost its sixth straight, 30-17, to Baltimore.

United Press International reported vendors outside Busch Stadium doing a brisk business selling bumper stickers inscribed "Trade Bidwill" and buttons saying "Bid Bidwill Farewell."

A St. Louis columnist suggested Bidwill sell the team as a public service because he was not spending enough to keep Coryell or such players as Terry Metcalf, now with the Toronto Argonauts of the Canadian Football League.

Wide receiver Mel Gray was quoted as saying, "We could go 0-16. It's a possibility."

Joe Sullivan, director of operations, said, "There's not much I can say to the fans, just that we're 0-6 and I thought we'd much better. I'm just disgusted., it's an ugly situation."

A crowd of 47,479 booed the Cardinals and cheered the Colts, except for former St. Louis cornerback Norm Thompson.

"I don't know why they'd boo me," Thompson said. "Everyone, I know wants to get away from Bill Bidwill. Why should they boo me for that?"

Running back Lydell Mitchell, traded to the Chargers after a salary dispute with the Colts, was in high spirits after the Charger victory. He carried the ball 19 times for 65 yards and caught nine passes for 51 yards.

"I finally felt like part of the offense," Mitchell said on the telephone about his third start. "Before, I might get stopped cold on my first or second carry and get to do nothing about it. I wasn't getting to play much.

"Sunday, on about my 10th carry, something started to happen. I like to carry the ball a lot and catch passes. I'm not old - I'm 29 and the weather out here is tremendous for players. Bumps and bruises heal quicker.

"This team's going to win. Coryell's a good coach. He instills confidence and prepares you mentally. Something that was lacking in the beginning is changing. Happily, it's not too late for good things to happen - making the playoffs. I strongly believe that."

Mitchell has been there, of course, three times with the Colts.

"It's like when Baltimore started out with a 1-4 record in 1975 and made the playoffs," he said. "Winning is contagious. These guys here have not been used to it. They're learning it's easier to go downhill than it was to climb uphill, when you get momentum.

"It's a shame we're 2-4. We could have been 5-1 or 6-0. We only had one bad game, against Green Bay. We have outplayed the opposition the other times."

Oakland beat the Chargers in the last 10 seconds on an intentional fumble game officials did not call.

Denver beat the Chargers their first meeting on a 75-yard punt return by Rick Upchurch with 3:17 remaining.

New England beat the Chargers in the last 31 seconds on a four-yard keeper by Steve Grogan.

"I caught a lot of third-down passes yesterday," Mitchell said. "(Quarter-back) Dan Fouts is getting used to me and I to him. We're getting a lot of unity.

"I got to admit the transition was not easy from Baltimore. You have self-doubts when you get traded - even though I asked for it. You wonder, 'Am I as effective as I used to be? Can I still do the things I used to do?"

My stats were not as good at first. I'd like to be where I've always been - in the Pro Bowl at the end of the season."

Mitchell helped provide ball control, as he did in Baltimore.

The Chargers had the ball for 45 minutes 17 seconds to the Broncos' 14:43, something Dallas could not do in the Super Bowl or Oakland this season and last year, or Pittsburgh and Baltimore last year. Denver had been outscoring opponents in the fourth quarter, 44-3, but San Diego won Sunday's final period, 6-0.

Coryell exlained the Charger strategy: "Against such a fine defense you have to be unpredictable. But after we got ahead we played a little more conservative, because it's an inpardonable crime to lose a game after you've had it won."

Mitchell said Coryell is a cheerleader. "When things are going bad he picks you up."

The team presented the game ball to Coryell, then owner Gene Klein asked the coach to give every player and assistant coach a game ball, 53 in all.

Asked about making the playoffs, Coryell said, "Why not? Even if our chances are one in 100 that's still a chance."