Every 30 years the Red Sox lose a playoff game to some short-stop who's Babe Ruth for a day.

In 1948 Lou Boudreau hit two homers against the Red Sox in leading the Indians to an 8-3 playoff win. Yesterday a soft-spoken island of calm in the Yankee sea of turmoil unloaded a three-run job on the screen at Fenway's Green Monster. It helped the Yankees win the Eastern Division title, 5-4.

The 26-year-old who won the 1978 division title in one swing - it was almost as dramatic as Bobby Thomson's homer against the Dodgers in 1951 - is named Russell Earl Dent. His trade name is Bucky Dent and his occupation is best shortstop in the American League.

Mike Torez was shutting out the Yankees, 2-0, in the seventh inning yesterday. They had two on and two out.

Mickey Rivers, the on-deck Yankee hitter, kneeled in the circle with the batboy, Sandy Sarandrea, 18, and held another bat for Bucky.

"This is the one he should be using," Rivers said. "I want to give him this one."

"We can't, said the batboy," he's hitting."

Dent swung and fouled a pitch off his shin. Rivers seized the moment.

"Now run up there and stick this bat in his hand and pull the other one away," Rivers said.

The red-haired batboy raced up to Dent, pushed the bat with Rivers' no. 17 on it into his hand and pulled away the other bat.

"Now go hit a home run," Rivers hollered.

Dent swung and delivered as ordered. The ball sailed in a huge curve from left center to left field, floated down on the top of the wall and rested against the screen. Home run. Three runs. And the Yankees were the East champs with a date tonight in Kansas City. Jim Beattie will face Dennis Leonard as the Yankees and Royals meet for the third straight pennant playoff. The Yankees won the first two with ninth-inning rallies.

Dent stood in the clubhouse, which looked with the Times Square subway stop at rush hour and smiled broadly as he recalled the magic moment. It was his fifth homer this year, 23rd of his big-league career and the only one he'll ever remember.

"I heard it, but I didn't see it," he said. "When it left the bat I thought it had a chance to hit the wall. I just ran hard to first. I didn't think it would clear the fence. I heard the silence of the crowd as I got to first.I knew it was a homer."

Among the Yankees, the Yankees of Billy Martin and Reggie Jackson and Thurman Munson and Catfish Hunter, Dent is almost an after thought. All he does is play a steady shortstop, hit his .240 and keep quiet.

"I was so glad when Billy left," he said. "It seemed that when Bob Lenon became the manager we could just concentrate on baseball."

Dent has always concentrated on baseball. He was a Little League star at home in North Miami, Fla, always dreamed of being a ball player and made it to the big leagues with the White Sox in 1973.

In 1977, a day before the season started, he was obtained from Bill Veeck in a deal for Oscar Gamble. It was standard practice these freeagent days. Dent was making $60,000 a year, wanted twice as much and threatened to play out his opinion. He was traded to New York and signed a three-year deal for half a million.

He batted .247 in 158 games last year as the Yankees won the world championship. He has played as well this year depite pulling a hamstring in July.

The Yankees were 14 back when Dent returned to the lineup regularly, just about the time Catfish Hunter began pitching regularly and Lemon became manager.

"Lemon gave me a chance to play myself back into shape," he said. "I don't know if Billy would have handled it that way.

"We won't have much time to celebrate this with the playoff against KC coming up," said Dent. "but there's a long winter ahead."

Not nearly as long as the winter in Boston.

Another hero for the Yankees was Rich Gossage. With runners on first and third, Carl Yastrzemski up and only the Eastern Division title in the balance, Gossage was invincible.

"That's what we got him out there for," said Lemon.

Gossage had relieved 25-game winner (now) Ron Guidry with one out in the seventh. The goose allowed five hits and a walk and had the tying run staring at him from third. He popped Yastrzemski up to end it.

Dent covered his eyes as third baseman Graig Nettles caught the ball. He couldn't watch.

"I felt like covering mine," said Gossage, "but I might have to run somewhere if he dropped it."

Gossage was the big man the Yankees wanted in the free-agent draft last fall. Scout Birdie Tebbctts, who watched him for a month in Pittsburgh in 1977, told the Yankees, "Don't let any other contender get him."

After a slow start, Gossage beat veteran Sparky Lyle, for the top bullpen job. He's pitched brilliantly, leading the league with 27 saves and posting a 1.91 ERA. All it cost the Yankees weas $2.85 million for six years, a bargain.

Gossage, a 6 foot-3, 210-pounder from Colorado Springs, Colo., throws a heavy ball, timed a 99 mph.

"Sometimes," he says, "I drop down to 90 or 92 mph if I get tired."

Gossage didn't get tired yesterday even though the Red Sox hit him freely. They didn't get the hit they needed.

"I think that's the only one that counts," he said.