The Yankees begin a three-game series in Boston tonight with a 4 1/2-game lead over the Red Sox in the AL East and a bit of their swagger back. They were reeling after losing twice to the White Sox, a potential October opponent, by a combined score of 24-4 and watching Roger Clemens and David Wells get battered.

"After what happened the first two nights, it was a big deal to win this game, especially with this series coming up," said Mike Mussina, who improved to 15-7 by allowing three runs and eight hits in six innings.

"No question this was big," Joe Torre said. "I don't care how good a team you are, you need to win to maintain your confidence. We needed a game we could play. We were out of the first two so quickly."

The Yankees scored five times in the first inning to erase a 2-0 deficit, with Ruben Sierra delivering a two-run single and Bernie Williams and John Flaherty adding RBI. Another run scored on a Chicago error.

Flaherty executed his second successful squeeze bunt of the season in the sixth, bringing home Aaron Boone, and Alfonso Soriano got a two-strike RBI single in the eighth. The Yanks won despite being outhit, 12-7, for the fourth straight game.

Now the Yanks' confidence "is right there," said closer Mariano Rivera, who notched his 29th save by recording the final four outs. "We won today, we battled. When we go there (Boston), it's different. It's energizing, it's good things."

Mussina, according to Torre, "sort of stabilized us going into this weekend," even though it wasn't a classic Mussina performance. The righthander left after six innings because Carl Everett's liner hit him on the left knee leading off the sixth. Mussina, however, said he'd be okay.

Everyone was, after the win. But there was little comfort during the game's later stages and the prospect of playing the sizzling Red Sox made Torre uneasy, as usual.

The Yankee bullpen was shaky again, with Jeff Nelson allowing two runs in the eighth to let the White Sox pull to within 6-5.

Nelson, according to Torre, "got so consumed with guys running on him that he forgot about pitching. He hung a breaking ball to Paul Konerko (who singled in a run) because he was concerned about Everett on second base."

After getting the final out of the eighth, Rivera allowed a leadoff single to Sandy AlomarJr. on a soft liner pastt Soriano. But Rivera struck out Alomar's brother, Robbie, and got Carlos Lee and Frank Thomas on long fly balls to center.

He showed, Torre said, a lot of movement on his pitches.

"I had a few days off and came back and felt good," said Rivera, who hadn't pitched since Monday. Then he added, referring to the infield single, "I wouldn't even call it a hit, but it was. You sit back and regroup and go at it. I don't let that frustrate me, because if I did that, we'd lose the game."

Even though he's struggled recently, Rivera seemed upbeat. He'll likely be a key figure in the series this weekend, which means his record against Boston bears watching: Two of his six blown saves have come against Boston and the Red Sox are batting .387 against him this season.

As always, Torre said starting pitching likely would dictate how the Yanks would play their rivals.

"We're fine," Torre said. "We all have questions — (Jose) Contreras is pitching (tonight) and we're all curious to see if he can repeat what he did against Baltimore. His confidence is much different than at any time during the year.

"When you go to Boston, it seems more than just a baseball game. ... I'm never comfortable going to Boston, in that park, to play that team.

"This is the best rivalry and it makes it that much better when you're fighting for first place. They've played very well lately. We built a lead and they came back. You know we're going in to play a hot ballclub."

Added Andy Pettitte: "It can change so fast if we go up there and they play great for three days and we struggle. But we're not worried about that too much."

Nor is Pettitte about his start against Pedro Martinez tomorrow. "If I get too hyped up for a game, that's when I get in trouble," Pettitte said. "This is what it's all about — the last month, trying to hold them off, trying to win this thing."