oe Morgan, 39, completed an outstanding comeback season today by hitting a two-out, three-run homer in the seventh inning that gave the San Francisco Giants a 5-3 victory over Los Angeles and eliminated the Dodgers from the National League West race.

With a victory, the Dodgers could have forced a one-game playoff with Atlanta, which finished the season one game ahead despite losing to San Diego.

The Dodgers were wrecked not only by today's loss, but by a late-season eight-game losing streak. They finished one game ahead of the third-place Giants, whom they had eliminated on Saturday.

"It's difficult. We had our chance to win," said Tom Lasorda, manager of the 1981 World Series champions.

Morgan's home run came a half inning after Lasorda pinch-hit unsuccessfully for starting pitcher Fernando Valenzuela with two outs, the bases loaded and the score tied at 2. In six innings, Valenzuela gave up two hits, struck out nine and had retired the last 10 batters he faced.

Asked why he pinch-hit for Valenzuela, Lasorda said he had no other choice after Valenzuela told the pitching coach his arm was tired.

But the Los Angeles Times quoted Valenzuela as saying through interpreter Jaime Jarrin, "My arm was okay. It was very well. It felt very nice."

Niedenfuer (3-4) was the new Dodger pitcher and the loser. He faced only three batters, getting one out and leaving runners on second and third for left-hander Terry Forster. After striking out pinch hitter Jim Wohlford, Forster had a 1-2 count on Morgan, a clutch hitter during Cincinnati's heyday. Forster threw Morgan a slider.

"It was . . . hanging," Forster said.

"I knew it was a homer as soon as I hit the ball," Morgan said.

Forster called the pitch "the worst moment of my career . . . It was the right pitch to make in that situation. But I hung it and I'll have to live with it."

Forster threw his glove in the air in disgust as the ball cleared the fence and Morgan slammed a fist in joy as he rounded second, while a Candlestick Park crowd of 47,457 cheered.

"When I was sitting in the dugout (earlier that inning), I was thinking that Ted Williams hit a home run on his last at bat," said Morgan, who is considering retirement. "Couldn't I be that lucky?"

He was.

"All that people would have been talking about, if we hadn't won this game, was how we folded and lost the last three games to the Dodgers," Morgan said.

Giants relief ace Greg Minton (10-4) pitched out of a bases-loaded, one-out jam in the seventh by striking out Bill Russell and retiring Jorge Orta, the pinch hitter for Valenzuela, on a grounder to Morgan at second. Orta's .154 average pinch-hitting this season was lower than Valenzuela's .172.

Bob Brenly opened the seventh with a single to center off Niedenfuer, and pinch hitter Champ Summers followed with a double to right. Niedenfuer struck out Minton before the Dodgers called in Forster.

The Dodgers scored their final run of the season in the eighth on one-out doubles by Ken Landreaux and Dusty Baker. But Minton prevented further damage by striking out Garvey and throwing out Rick Monday on a grounder back to the mound.

Los Angeles took an early lead when Ron Cey hit a two-run homer in the second off starter Bill Laskey.

But the Giants tied the score in the bottom of the second after loading the bases on a single by Darrell Evans, a double by Jeff Leonard and a walk to Brenly. Valenzuela (19-13) walked Johnnie LeMaster to force in a run, and Leonard scored when Laskey hit into a double play.