Not since 1956 have two New York baseball teams met in postseason play, or in what has been known for much of the century as a subway series. It was so long ago, when the Yankees' Don Larsen pitched his perfect game that October against the Brooklyn Dodgers, the games then weren't known as the postseason. Anything after the regular season, barring a tie for first place, was the World Series.

Now there are series and series and series to determine baseball's champion. But even so, with the Yankees and the Mets in the first round of playoffs creating simply the possibility of two New York teams meeting again in a World Series for the first time in 43 years, this city is abuzz. "Every place you go you hear about it," Yankees Manager Joe Torre told reporters. The tabloid New York Post has adopted a logo, "Subway Series, Here We Come," based perhaps on the Yankees' status as defending champions, the Mets' history of accomplishing the improbable and wishful thinking.

"There's a lot of excitement--but there's still a long way to go. The Yankees have a much greater shot than the Mets," said Ralph Branca, the onetime Dodger who delivered the pitch that the New York Giants' Bobby Thomson turned into the "shot heard 'round the world." Yes, there were three New York teams then, in 1951. And perhaps in a foreshadowing of unlikely triumphs by future Mets teams, the Giants overcame a 13 1/2-game deficit to force a best-of-three playoff for the National League pennant and the right to play the Yankees, who won almost all the intracity matchups back then.

Thomson, who was born in Scotland and grew up on Staten Island, hit a 1-1 pitch for a three-run homer with two out in the bottom of the ninth to give the Giants a 5-4 victory and the pennant. This October epic occurred at the Polo Grounds, which used to be in Manhattan, across the river from Yankee Stadium. "I got over it 10-15 years later," said Branca. "When I got to be 45, it didn't hurt any more." But New Yorkers suspect that, really, Branca never has gotten over it.

As the father-in-law of Mets Manager Bobby Valentine, Branca has a clearly defined interest in one of the city teams. He takes a dim view of the New York media, which has criticized Valentine while often noting his career total of games managed, 1,704, without making the postseason before the Mets beat Cincinnati on Monday in a one-game playoff for the NL wild-card spot. "Bobby is maligned, he's unfairly criticized," said Branca, sounding outraged. "Bobby's Bobby--he draws lightning. But I love him, warts and all. And there aren't many warts when it comes to baseball. When it comes to baseball, he's a PhD."

But managers always are second-guessed, and nowhere more than in New York. The late Dodgers manager, Chuck Dressen, is second-guessed to this day for bringing in Branca to face Thomson--that's how it can be in a subway series. New Yorkers never forget. And if the winners are feted with ticker-tape parades, the losers and their fans often are doomed to suffer their regrets for a lifetime.

Things used to happen to Brooklyn that could only happen to Brooklyn, or so it seemed. There are Yankees fans who would agree with Dodgers fans that the called strike on Dale Mitchell to end Larsen's perfect game was a ball. And where else but Brooklyn could Dodgers catcher Mickey Owen let a third strike get away from him in what would have ended Game 4 of the '41 Series with the Dodgers winning, instead of letting the batter reach first on a passed ball and setting up a victory rally for the Yankees? But nothing matched Thomson's shot of '51.

"I include Don Mueller as part of what happened," Thomson said this week as he watched the Yankees' and Mets' playoff games on television. Mueller had "half killed himself" sliding into third base, creating a delay. Thomson, the next batter, stood near third, concerned about his teammate, who finally was taken off on a stretcher and replaced by a pinch runner. "I started to walk back to the plate and Leo [Durocher, the Giants' manager] said to me, 'Bobby, if you ever hit one, hit one now.' I didn't even look up at him. I thought to myself, 'Leo, you're crazy.'

"I had been distracted by Mueller. I realized I'd better get back to work. I had to psyche myself up. I called myself an s.o.b.--'C'mon, you s.o.b.' I'd never done that. It's funny how instinct takes over. People have asked me, what did I think of the crowd then? I didn't even hear the crowd. I was in the park by myself.

"When I got to the plate, I looked up and there's Branca. I didn't know they made the change. I just wanted to wait and watch, give myself a chance to hit. I took the first pitch for a strike. The next pitch he came inside with a fastball. It was a ball, but it wasn't that bad. It was like a blur. I got a glimpse of it and I jumped on it. I was pretty quick with my hands. When I saw it going I thought home run, but then it started sinking. I thought, 'Stay up.' I've heard that Branca was on the mound saying. 'Sink, sink, sink.' "

The ball barely made it into the seats. The Dodgers were doomed again. Giants broadcaster Russ Hodges screamed to the radio audience: " . . . It's gonna be . . . I believe. . . The Giants win the pennant! . . . the Giants win the pennant! . . . The Giants win the pennant! . . . Bobby hit into the lower deck of the left-field stands! . . . The Giants win the pennant and they're going crazy! . . . I don't believe it! . . . I don't believe it! . . . I will not believe it! . . ."

The rivalry between the Yankees and the Giants began with three straight subway series from 1921 to '23, with the Giants winning the first two as the Yankees rented space from them in the Polo Grounds. In 1923, the Yankees opened their own stadium just a short walk away and beat the Giants in that Series. In all, there have been 13 World Series played entirely in New York. From 1947 through 1956, seven subway series involved the Yankees, Dodgers and Giants.

Former Yankee Whitey Ford holds numerous World Series pitching records, having appeared in 11 Series between 1950 and 1964. "I'd be tickled if both the Mets and the Yankees played in the World Series," Ford said. "In the National League, I root for the Mets. But if they play the Yankees, I'm for the Yankees." Ford added: "I've never cared much about personal records, but the one that means more to me than any was breaking Babe Ruth's scoreless innings streak."

In 1918 Ruth reached 29 scoreless innings pitched in World Series play for the Boston Red Sox, breaking the record of 28 set by Christy Mathewson. Ford was stopped at 33 during the 1962 Series. According to Robert Creamer in "Babe: The Legend Comes to Life," Ruth had similar feelings about his scoreless streak. "Of all his accomplishments in baseball it was the one of which he was most proud," Creamer wrote.

Up in the Bronx now, there is a palpable concern about the Mets, who have made the postseason for the first time in 11 years. Yankees executives who have offered good wishes to the Mets have been greatly restrained.

"They're a great team," said Yankees General Manager Brian Cashman. "[Mets General Manager] Steve Phillips and their ownership over there have done such a tremendous job in putting that club together, and it's a scary team. I'm sure those National League opponents they're going to have to go through, they're not comfortable facing them. I'm certainly rooting for them, but I have enough problems."

It's probably crossed Cashman's mind what life might be like with the Yankees' volatile owner, George Steinbrenner, should his club lose a subway series. "God, if we lost to the Mets," a Yankees executive told Newsday, "I wouldn't want to be around the office for a week." That might have been an understatement.

CAPTION: With Yankees Whitey Ford, left, and Mickey Mantle, a subway series against the Giants or Dodgers was a frequent occurrence in the 1950s. Of the New York teams of 1999, Ford says, "I'd be tickled if both the Mets and the Yankees played in the World Series."