The Los Angeles Dodgers traded a nine-year mainstay of their pitching staff, right-hander Bob Welch, to the Oakland Athletics yesterday in a three-team deal that made New York Mets left-handed reliever Jesse Orosco a Dodger.

In the eight-player trade, announced after many baseball people had left Dallas following the major league meetings, Oakland received Welch and left-handed reliever Matt Young from the Dodgers in exchange for shortstop Alfredo Griffin and right-handed reliever Jay Howell.

The Mets received minor league pitchers Jack Savage from the Dodgers, Kevin Tapani and Walt Whitehurst from the Athletics.

Welch, a 1978 World Series sensation now 31, recovered from arm trouble and a drinking problem to post a 15-9 record with a 3.22 earned run average as a starter in 1987 for a career 115-86.

Orosco, 30, was a hero of the 1986 National League playoffs and World Series, but tailed off to 16 saves, 3-9, 4.44 ERA in 1987.

The Dodgers have had trouble at shortstop for several years, and hope Griffin, 30, is the answer. The former Toronto star's best season was 1986 (.285, 33 stolen bases); in 1987 he drove in 64 runs for Oakland.

Howell, 32, has had an up-and-down career, mostly in relief, with two all-star appearances. Young, 29, a former starter turned to relief in 1986 with Seattle, was a 1987 Dodgers disappointment . . .

The Mets made another trade, shortstop Rafael Santana to the New York Yankees with minor league left-hander Victor Garcia for three prospects: catcher/outfielder Phil Lombardi, outfielder Darren Reed, left-handed pitcher Steve Fry . . .

The Yankees' prized free-agent reliever Dave Righetti on what he termed a "mind-boggling" offer -- reportedly as high as $20 million over three years -- to pitch in Japan: "It's a tough thing to do, to pick up and leave the country, and I'm rather confused. I know it would be a huge adjustment, but I think I can handle it."

Righetti made $800,000 this year and reportedly is asking the Yankees for about $1.5 million a year for three years.

Said Yankees owner George Steinbrenner: "It's a chance to see if it's only money {he wants}. They all talk about Yankee pride and loyalty. Well, if it's only money, then he's got to go."