In April this year, Brian Doyle didn't expect to play in the major leagues. He was a second-stringer in the bushes.And some people believe he never again will play for the Yankees. But for now, in the happiest story of all, the little man from Kentucky is a World Series hero.

Champagne bottle in hand. Reggie Jackson was celebrating. This was a minute after the Yankees won the Series the other night. Jackson was huge again when it mattered most, leading the Series in runs batted in. The leading hitter, by average, was Brian Doyle at .438 on seven hits in 16 at-bats. He had three hits in each of the last two victories. His double tied game six early and a single later made victory certain.

"Who won the MVP?" Reggie Candybar was shouting. A sports magazine gives a car to the most valuable player in the Series. A year ago, Jackson was it and this time Reggie was stumping for kid. "Who's the MVP? Brian Doyle! How about Brian Doyle!?"

And Mr. October, laughing out loud, hugged Mr. Who.

"It's unbelievable, it really is," Doyle said, cradling his own bottle of bubbly. Twenty-three years old, 5 feet 10, 165 pounds (not counting the estimated five-pound chaw of tobacco), Brian Doyle is a husband, father, born-again Christian who told the curious before the Series, "I've never been nervous in baseball and there's no reason to start now."

People nodded and said, sure, sure. But the kid was right. And of all the ironies that accompanied the Yankees' victory, none is more profound than Brian Doyle's exhilarating moment in the sun. The Yankees won with Bucky Dent as teh MVP?" Bucky Dent ?

The ace, Ron Guidry, won though he walked eight. A rookie from Dartmouth pitched the first complete game of his major league career. Good heavens, the Yankees won without Willie Randolph, only the league's All-Star second baseman.

Bye-bye, Mr. All-Star. Hello, Mr. Who.

During last year's Series, Brian Doyle was selling suits and ties in downtown Bowling Green, Ky., maybe 15 miles from his hometown of Cave City, population 2,100. He comes from a baseball family. His father played amateur ball, his twin Blake is a second baseman on Baltimore's top farm team and his older brother, Denny, was a major league journeyman who achieved prominence for the Red Sox in the 1975 Series.

THis was Brian's sixth season as a pro, but in April, when he was ot invited to the Yankees' training camp, he was sent to Tacoma of the Pacific Coast League. At first a utility man, he became a regular and twice was called up to the Yankees when first Randolph and then Dent were injured.

Doyle returned for good - "I was on a roller coaster, but it was fun" - when the rosters grew to 40 players in September. As insurance, he was kept on the playoff roster.

Then Randolph hurt a leg and Doyle became the Yankees' second baseman against right-handed pitcher. He'd been in the big leagues 105 days, but went to bat only 52 times, getting 10 hits for a .192 average. In the playoff, he drove in a run, his first and only RBI before the Series.

So everyone wondered, when the Series began, if Brian Doyle, all blond hair and blue eyes and innocence, would be nervous. He insisted not. Don't believe the evidence of tap-tap-tapping feet during an interview. Just eager to play, he said, not nervous. Sure, kid. Just don't swallow your tobacco in the clutch.

He didn't. As Bobby Richardson brought style and class to second base for the Yankees, so did Doyle.

He'd been hired for his good glove. "And instead of worrying about what 'people' think, I just want to prove to my teammates I can put the bat on the ball," he said before game one.

So the kid who had 10 hits in 105 days had seven in the six-game Series, five in a row in the last two victories. Besides the two RBI, he scored two runs in the 7-2 victory that sent Reggie looking for the champagne.

While the Dodgers' veteran infielders seemed novices in the nuances of a ground ball. Doyle was flawless. He handled 23 chances without an error. He was in on six double plays - the whole L.A. team made only four - and, in a small bit of the inflieder's art that is often overlooked, Doyle made swift tags on would-be base stealers, slapping catcher Thurman Munson's weak throws against four runners.

Dick Howser, the Yankees' infield coach, knew in May that Doyle was extraordinary. The kid booted two ground balls in Chicago and Billy Martin, then the manager, sent Howser to Doyle.

"I told him Billy was upset," Howser said. "He just looked at me and said, 'Look, I made just four errors last year. Brian is very confident, very professional.

"I'm ticked to death for this guy now. All the other guys get the ink, but he and Dent proved there are places for the kid that just does his job instead of popping off all the time. There's always room on a team for a guy like him. He just works and works and he's got such a great attitude."

The winner's share in the Series may exceed $30,000 a man. Doyle's salary is probably about $15,000 a year. Will he get a full share of the Series money or, since he was with the team only part time, a fraction of a share?

Doyle once worked as a truck-body builder and football official to supplement his $500 a month salary in Class A ball at Lynchburg, Va. He says he doesn't know how much money the Series will mean to him. And he doesn't care.

"Whatever it is, it'll be more than I was expecting in April," he said.

By then, he had opened his bottle of champagne.

"It feels great," he said, smilling, "to be a world champion." And, to newspapermen he said, "Fellas, let's cut it. This is my first one and I want to enjoy it."

The kid took a drink of champagne.