The Red Sox’ 5-4 win over the Yankees was a rare triumph indeed - in fact, it was one-of-a-kind.

The Red Sox trailed, 4-2, entering the ninth against Yankees closer Mariano Rivera. But the future Hall of Famer gave away the lead when Jason Bay battered a ball to left-center, barely clearing the Green Monster for a game-tying two-run homer.

The game continued into the 11th, when Kevin Youkilis jumped on a 2-2 fastball from reliever Damaso Marte and launched the ball onto Lansdowne Street for a game-winning solo homer. The Sox had a victory that was unprecedented in their long history against the Yankees.

Among the 1,995 games (excluding ties) between the eternal rivals, this was the first time that the Sox had hit a game-tying homer in the ninth and then hit a walk-off homer in extra innings.

This was the first time the Red Sox beat the Yankees with a walk-off homer during the regular season since Bill Mueller’s legendary homer against Rivera on July 24, 2004.

Yet in some respects, the game never should have gotten to the point where such late-inning drama would be necessary. The Sox spent most of the game wasting tremendous opportunities, going 2-for-14 with runners in scoring position through the first eight innings.

Time and again, the Sox hit into double plays – four of them, to be exact – that killed potentially game-breaking rallies. The team had Joba Chamberlain on the ropes, but a pitcher who had never gotten more than two double-play balls in his career kept getting inning-ending twin killings from the Sox.

“Early in the game, it seemed like we had a million chances,” said Dustin Pedroia. “It was definitely frustrating. It seemed like it was one after the other. But he did a great job of throwing to certain spots…It seemed like they turned 100 (double plays), to be honest with you.”

Yet while the Sox failed to take advantage of their scoring opportunities early, the Yankees proved unable to do so in the later innings. In the seventh, the Yankees had the bases loaded and no outs, and managed to plate just one run. In the ninth, they had the bases loaded and no outs, and failed to score.

New York went 4-for-19 with runners in scoring position. They left 15 men on base.

“We were able to steal one,” said Sox catcher Jason Varitek.

In doing so, the Sox exchanged a defeat that could have been immensely frustrating for perhaps their most improbably regular-season victory over the Yankees since 2004.

Here are five things we learned over the course of that wild ride:

1) THE RED SOX DO NOT OWN RIVERA…BUT PERHAPS THEY LEASED?

In his career, Mariano Rivera has 486 saves. When entrusted with a late-inning lead, he has sealed the deal 89 percent of the time, with a relatively scant 61 blown saves spread over his 15 seasons.

Yet almost 20 percent of those blown saves have come against the Red Sox. After Jason Bay’s two-out, two-run homer in the bottom of the ninth against the Yankees closer, Rivera has now blown a dozen leads against the Sox. Despite that record of success, the Sox were hardly crowing.

“We have put a dent in him probably more than anybody else, but again, we’ve had more opportunities. That’s not so good either. If he’s out there, something’s going right for them,” said Sox manager Terry Francona. “When you see him come in, it’s not a confidence booster.”

“He’s the best closer ever to pitch. You go up there and battle,” added Youkilis. “Hopefully he leaves something over the plate. He doesn’t do it a lot. Just a little bit over a long period. He probably has our number way more than we have their number.”

Rivera had been called upon for his first four-out save of the 2009 season after forging a 0.38 ERA in 15 appearances of more than one inning last year. He struck out the first two batters he faced (Dustin Pedroia to end the eighth, and David Ortiz to start the ninth), but Youkilis jumped on a cutter and drove it up the middle, and then Bay absolutely unloaded on a cutter up in the zone for his first ninth-inning gamey-tying or go-ahead homer as a member of the Sox.

“I just made a bad pitch,” shrugged Rivera. “That’s all it is. If I made my pitch, it’s a little bit different.”

It would be a mistake to say that the Sox no longer fear, respect or submit to Rivera. Friday marked his first blown save against Boston in two years, dating to April 20, 2007. Overall, it was Rivera’s first blown save since last August 12.

So the Sox have no illusions about dominating Rivera. But they do still believe that success against him is within their grasp.

“He’s still not a comfortable at-bat,” said Mike Lowell. “It’s not like he comes in and we’re like, ‘Ha, ha! Look how fun this will be.’ But guys understand their strengths, and are able to put some good at-bats together. That’s the personality of the lineup.”

2) THE MANTLE OF THE MOST FEARED RED SOX HITTER HAS BEEN PASSED

Looking for a walk-off? It used to be that the Red Sox would want only one man at the plate in those situations. David Ortiz seemingly claimed exclusive province over the game-winning, game-ending hit.

Ortiz has 16 career walk-off hits in the regular season, and a few more in the postseason. He will always be thought of as one of the great threats in the game when the game is on the line.

But it’s been a while since Ortiz has been that guy. Of his 16 career walk-off hits, none has come since the 2007 season (a homer that year against Tampa Bay won a game on Sept. 12), and he’s had just that one since August of 2006.

And so, a once-unthinkable event — Ortiz striking out on a nasty Damaso Marte slider in the bottom of the 11th in a tie game — was not nearly as shocking as it once might have been.

For that matter, the fact that Ortiz had barely completed his journey back to the dugout before Kevin Youkilis cleared the Monster Seats was also anything but unexpected.

“Youk’s been on fire all year long,” said Pedroia. “He’s unbelievable right now.”

On a night when Ortiz went 1-for-6 with four strikeouts, Youkilis went 2-for-4 with two walks. He is now hitting .433 with a .534 OBP and 1.317 OPS.

The walk-off was huge, but his ninth-inning hit was perhaps even more significant. His single to center set up Bay’s eventual game-tying homer.

Clearly, Youkilis is a player who is capable of performing at an exceptional level in a game’s white-knuckle situations. A year ago, Youkilis hit .358 with a .425 OBP and .660 slugging mark from innings 7-9, often against the best relievers an opponent had to offer.

“That’s more the consistency of being a quality hitter,” said catcher Jason Varitek. “You can’t all of a sudden make yourself a better hitter in those situations. Youk’s a good hitter.”

The 30-year-old has become the player whom the Sox want to see at the plate with the game on the line, and the one who is most feared by opponents. With right-hander Joba Chamberlain on the mound, the Yankees elected to pitch around Youkilis twice and attack left-handers Ortiz and J.D. Drew.

Ortiz has now gone eight straight games without walking, tied for the fourth longest streak of his Red Sox career. It’s hard to blame other teams for trying to attack him in an effort to avoid pitching to Youkilis with a man on base.

3) DON’T FORGET THE DEFENSE

The Sox never would have been positioned to claim their remarkable comeback without a slew of web gems:

Third inning: Nick Swisher stepped to the plate with two on and two out. The switch-hitting Swisher (battting right-handed) ripped a 92 mph fastball down the left-field line. But Mike Lowell dove and speared the ball, robbing Swisher of a run-scoring double and ending the Yankee threat.

Seventh inning: the Yankees had the bases loaded and one out. Robinson Cano’s looper seemed destined to scrape the grass, but instead, Jason Bay ranged far to his left and dove, plucking the ball just before it hit the turf. While a run scored on the sac fly, the brilliant play prevented the Yankees from achieving a potentially huge inning.

Ninth inning: Javy Lopez could not locate, filling the bases by putting the first three batters of the inning on base (hit batter, walk,  walk). But Lopez got Cano to hit a sharp bouncer to Dustin Pedroia, who was playing in. The 2008 Gold Glover fired home, and Jason Varitek relayed the ball to first for an unconventional 4-2-3 double play that kept the game within reach for the Sox.

“It was kind of perfect,” said Pedroia. “He hit the ball so hard, it was just kind of right at me.”

“It was key,” added Jason Varitek, “that we were able to keep that game at arm’s reach.”

Tenth inning: With a runner on second and one out, Derek Jeter hit a sharp grounder up the middle. Dustin Pedroia made a diving stop to his right to vacuum the ball, jumped up and fired to first for the out. A potentially run-scoring hit was instead an out.

“Right spot, right time,” shrugged Pedroia.

Eleventh inning: With a runner on first and no outs, Nick Swisher, who has all of four sacrifice hits in his career, pushed a bunt too hard at first baseman Kevin Youkilis. The 2007 Gold Glover pounced and fired to second to cut down Posada for an out. The play proved huge, since Robinson Cano followed by slashing a one-out single to right. A potentially run-scoring hit instead put runners at first and second. The next batter, Melky Cabrera, then grounded to second for an inning-ending double play.

It’s early – probably too early to draw any real conclusions about the Red Sox defense. But the team does have a pair of Gold Glovers on the right side of its infield, another former Gold Glover at third and a player in center (Jacoby Ellsbury) who is an exceptional ball tracker.

Thus far this year, the Red Sox defense has been extremely successful at turning batted balls into outs. Entering Friday’s game against the Yankees, Boston had turned 70.6 percent of balls in play into outs, the second-best mark in the American League and the seventh-best in the majors.

“Defense is going to win games. That’s what we rely on, pitching and defense,” said Youkilis. “We’ve got a good pitching staff, and we’ve got a lot of guys out there who can play good defense. Mike Lowell, Pedroia made that great play, Jason Bay made that diving play. That’s how you win ballgames.”

4) THE YANKEES ROTATION COULD BE IN TROUBLE

The Yankees place Chien-Ming Wang on the disabled list due to weakness in the adductor muscles of his hips. That followed an outing in which starter Joba Chamberlain was thoroughly underwhelming.

Chamberlain threw 91 pitches. The Sox swung and missed just three of those (one fastball, one curve, one slider). The pitcher allowed nine hits and four walks while striking out just two. Though he was able to hold the Sox to just two runs (one earned) thanks to an unbelievable yield of four double-play balls, it seemed clear that he is a different, and more vulnerable, pitcher than the familiar flame-thrower of the past two years.

“It’s a tough lineup. It’s hard to pitch those guys. They’re very good at what they do. You’ve just got to be more consistent and be down with those guys,” said Chamberlain. “The balls that got hit were up. I’ve just got to continue to get down and I made some decent pitches when I needed to get out of innings with double plays.”

One member of the Sox credited Chamberlain with pacing himself over his outing. But with his fastball velocity down from the mid- and high-90s to, more often, 92-93 mph, the consequences are far-reaching.

If Chamberlain cannot generate swings and misses, he will give up hits and walks as opposing batters are able to work deeper into counts. It is worth noting that Chamberlain has now given up nine walks in his past two starts, spanning a total of 10 innings.

On Friday, the bullpen had to pick up six innings of slack following his effort. Clearly, that is not the best formula for the Yankees to find their way to a victory. Until Chamberlain can replicate at least a hint of his dominance as a closer, we will represent a weakness in the Yankee rotation at a time when Wang’s injury suggests they cannot afford one.

That said, it is worth noting that the Yankees – like the Sox – have potentially outstanding rotation depth in the minors. Phil Hughes (3-0, 1.86 ERA) and Ian Kennedy (1-0, 2.00) have been dominant this year.

5) JULIO LUGO IS ALMOST HEALTHY. WHAT HAPPENS WHEN HE IS?

Manager Terry Francona reiterated before Friday’s game that Julio Lugo could be activated from the disabled list as soon as Monday against the Indians. But will the Sox want to tinker with the presence of current shortstop Nick Green in the lineup in the short-term?

Green went 2-for-4, and had a key game-tying (at the time) hit against Chamberlain. He is now hitting .333 with a .400 OBP and .556 slugging percentage this year.

Green’s career track record suggests that this run will not be sustainable. Nonetheless, it will be interesting to see the degree to which the Sox keep him in the lineup once Lugo is activated.

BONUS ODDS AND ENDS

Mark Kotsay took batting practice and threw on the field. He will work out at Fenway over the coming days as a prelude to a rehab assignment that could potentially begin as soon as Thursday with Triple-A Pawtucket ... As expected, the Sox activated Jonathan Van Every from the disabled list to fill in as an outfield reserve and pinch-runner. Van Every, who got the Sox' last walk-off hit against the Yankees in the final game of the 2008 season, entered on Friday as a pinch-runner ... Rocco Baldelli threw on the field and did some hitting for the first time since going on the disabled list with a sore hamstring. He still has yet to run, and is unsure when he will take that step. The outfielder said that the issue was unrelated to his channelopathy. "It doesn’t have anything to do with the word you (reporters) like to write: fatigue,” he said ... For the first time in his major-league career, spanning 139 regular-season appearances, Hideki Okajima failed to record an out. He gave up two runs on four hits.