Roger Clemens was back in familiar surroundings today. There was a visit with wife Debbie to the Boston suburbs he once called home and time spent with former Red Sox catcher Rich Gedman and, finally, a drive down the Mass Pike to Fenway Park.

"It was really a beautiful trip in here from Framingham," Clemens said. "Debbie noticed it too--how great everything looked. We'd forgotten how beautiful New England is in the fall. Rich told me I probably didn't appreciate it as much when I was playing here. I think that's true."

Later, on the day before one of the most important moments of his 16-year career, baseball's dominant pitcher of his generation seemed completely at ease roaming the hallways and concourses of Fenway Park, nodding at some Red Sox employees, calling others by name.

"I think I'll be relaxed," Clemens said, "because I know the environment."

In one of the magical moments of this or any other baseball season, Clemens will share the stage with Boston right-hander Pedro Martinez Saturday afternoon when the Boston Red Sox and New York Yankees play Game 3 of the American League Championship Series.

"I don't know what's going to happen," Yankees Manager Joe Torre said, "but it's going to be a helluva experience. It's going to be electric."

With the Yankees having won the first two games of the series at Yankee Stadium, the Red Sox desperately need a victory to have any chance of making their first World Series appearance since Clemens led them there 13 years ago. For the Yankees, the game simply is one more opportunity to show the world that they remain the best team in baseball.

But for once, a spot in the World Series is less important to millions of baseball fans--especially New Englanders--than the sight of having Clemens return to Fenway Park wearing the uniform of the hated New York Yankees. As if that weren't enough, the Red Sox are sending baseball's best pitcher of 1999 to the mound.

"This is what every baseball fan in New England has been waiting for," said Red Sox infielder Lou Merloni, a native New Englander. "They've been waiting three years to see Pedro pitch against Rogers."

One fan is willing to part with four good seats to Saturday's game. Price: $12,000.

Clemens was booed loudly during this summer's All-Star Game at Fenway Park and expects more of the same Saturday afternoon. After 13 seasons in which he won three Cy Young Awards and 192 games while leading the Red Sox to three playoff appearances, Clemens had a nasty departure after the 1996 season.

After negotiations with the Red Sox fell apart, Clemens signed with the Toronto Blue Jays. Red Sox General Manager Dan Duquette seemed almost happy about ushering Clemens out of town, telling fans that Clemens was in the twilight of his career.

Clemens proved Duquette wrong by winning two more Cy Youngs and 41 games in two seasons with the Blue Jays. Then, last spring he accepted a trade to the Yankees because he believed it offered him the best chance of finally winning a World Series.

Now, his time has arrived.

Problem is, he's going against the guy who won the American League's triple crown of pitching: victories, ERA and strikeouts. A back injury sidelined Martinez early in Game 1 of a first-round series against Cleveland, but he came in from the bullpen in the decisive Game 5 and threw six no-hit innings for the victory.

"It is not 100 percent yet," Martinez said. "But after pitching in Cleveland, having seen the result, I don't think I need my full strength to be a pitcher or to be able to beat another team. Every pitcher is going to tell you that maybe three or four or five times a year, you pitch 100 percent fine. The rest you pitch lacking something. I am going to deal with this, and I am not going to bring up the fact that I hurt myself."

When Duquette acquired Martinez, it was to replace Clemens as the staff ace. Martinez has more than done that, going 43-11.

Now, here they are together in baseball's most beautiful ballpark, the one crammed between Yawkey Way and Landsdowne Street, the one with the Green Monster and the ladder in left field, the one where fans are close enough to carry on conversations with players. It's the park that has inspired poetry and novels and documentaries.

The Yankees believe if Clemens controls his emotions, as he did in pitching seven shutout innings against Texas last week, he's still as good as any pitcher in the game. But the trick will be in keeping him calm.

"I'll have so many emotions I'll have to curtail somehow," Clemens said. "It'll be exciting. I'm looking forward to it. I don't think I'll be able to afford too many mistakes going against Pedro. Only thing I can hope is that he'll have a little hiccup. I think my mistakes are going to have to be very minimal. I know they're going to come at me, and I'll come at them. That's the way it's supposed to be."

Meanwhile, there are no such questions regarding Martinez, who struck out 17 Yankees--a Yankee Stadium record--in his last start against the New Yorkers.

Both pitchers should be assisted by the 4 o'clock start time, meaning hitters will be standing in shadows part of the afternoon.

"It just means you can't see," Red Sox shortstop Nomar Garciaparra said. "Other than that it'll be fine."

As both teams visited Fenway today, they emphasized that fans and the media were more caught up in the pitching matchup than the players were. For the players, who are not as aware of 80 years of bad feelings, it's more a day at the office even though a cake was delivered to the Boston clubhouse with the words: "Kill Those Yankees."

"Players don't really get into that stuff," said Red Sox third baseman John Valentin said. "You may think I'm lying about that, but we just focus on how he's pitching--not who's pitching."

CAPTION: "I am going to deal with this, and I am not going to bring up the fact that I hurt myself," Pedro Martinez says of back.