The bats -- led by Youkilis and a host of other heroes -- belted A.J. Burnett around the yard.
"Youk was awesome," said Red Sox second baseman Dustin Pedroia. "That's why he's one of the best. We scored some runs early and kept going."
Meanwhile, from the mound, Junichi Tazawa belied his youth (23 years old) and lack of professional experience (none before this season) by firing six shutout innings en route to his second Major League win. Tazawa scattered eight hits, walking two and striking out two.
"Like I told you guys, when we get our pitching stopping their offense, things are going to happen. That's what happened today," said Red Sox slugger David Ortiz, who pummeled home run No. 20 on the season, a line shot over the Monster.
This was one to savor for the Red Sox, particularly if they can parlay it into some sustained momentum, which had been elusive in the 15-18 stretch that preceded Saturday.
"I thought we showed up with great energy, and that's important after a night like last night," said Red Sox manager Terry Francona. "And certainly getting runs early helps. They show up and play, and we played better today than we played yesterday."
Boston trimmed New York's lead to 6 1/2 games in the American League East entering Sunday night's rubber match, which features a glittering pitching matchup of Josh Beckett and CC Sabathia.
The victory also increased the Red Sox's AL Wild Card lead to two games over the Rangers, who lost, 5-4, to the Rays in 10 innings.
Tazawa, a right-hander who was pitching in the industrial leagues of Japan at this time a year ago, navigated out of several jams and finished his day by inducing Melky Cabrera to ground into a 4-6-3 double play on pitch No. 99.
"I felt more relaxed as the team got more runs," said Tazawa. "But I knew their offense was really good, so I just stayed focused on taking outs from them."
Though Burnett was nothing short of masterful against the Red Sox on Aug. 7, allowing one hit over 7 2/3 shutout frames, this marked the third time he has been shelled at Fenway this season.
Pedroia, Victor Martinez, Ortiz and Jason Bay all had multihit games.
The offense started early and never really stopped.
With runners at the corners and two outs in the first, Ortiz went with the pitch, lining a two-run double off the Green Monster. Bay then looped a single into left and Ortiz rumbled home from second to make it 3-0, Boston.
"We scored 11 runs yesterday. We went out today and scored, what, another 14?" said Ortiz. "Like I said yesterday, we're going to hit. We're swinging the bat pretty good."
The Red Sox then made an even louder statement against Burnett in the bottom of the third. Alex Gonzalez hit a one-out solo homer, his first long ball since rejoining Boston a week ago. With two outs, Burnett lost his control, walking Pedroia and Martinez. That turned out to be highly costly, as Youkilis pummeled a three-run shot to left-center, giving Tazawa a commanding 7-0 lead.
The Yankees had some chances, putting two on with one out in the first, doing the same thing in the fourth, and getting two on with two outs in the fifth. Each time, however, Tazawa made the pitches he needed to escape.
"We had people come up with big hits today," said Red Sox catcher Jason Varitek. "You need those, and we made big pitches to complement the big hits."
While the big hits were delivered by the usual suspects, the pitches were delivered by a seemingly nerveless rookie who spent most of his season at Double-A Portland.
"What he's done in a very short period of time is impressive," said Red Sox pitching coach John Farrell.
Burnett briefly regrouped in the third and fourth, holding Boston scoreless. But Ortiz ended that with his two-out solo shot in the fifth. It was the seventh consecutive 20-homer season for Big Papi, who has 19 long balls since June 6.
"I'm just going to keep on swinging and let things happen," said Ortiz. "You guys know the first two months of the season were really tough on me. I'll just put those in the past and do what I can do right now."
Much like Ortiz, Boston's offense as a whole has had some peaks and valleys in recent weeks. But this much is clear. The bats look nothing like the bunch that somehow went 31 innings without scoring a run during that four-game sweep in New York two weeks ago.
"That's a really good team," Yankees first baseman Mark Teixeira said. "I mean, that team can score runs with the best of them. A.J. was going after them, and they were hitting. You've got to give them credit."