BOSTON -- To achieve something that hasn't been done in the history of a 117-year-old organization, it makes sense that a team would have to put in a little overtime.

For the Boston Red Sox, it was mandatory.

The Red Sox have scored fewer runs than the New York Yankees. By run differential -- the measure that many statheads use to determine if a contender is for real -- the Sox are worse than the Yanks. And in the 19-game season series between the American League East rivals, the Red Sox went 8-11 and were outscored by an 82-59 margin.

Yet it is Boston -- not New York -- on the verge of clinching the division title, marking the first time since divisional play began in 1969 that the Sox will have won back-to-back AL East crowns.

So, how did they do it?

Start with a 15-3 record in extra-inning games.

"It's probably one of the main reasons we sit here today," manager John Farrell said.

The Red Sox have tied a franchise record for extra-inning wins, matching their total from 1943. They have won their past seven games that have gone beyond the ninth inning. Their collection of extra-inning triumphs includes 12-inning (April 5 vs. the Pittsburgh Pirates; June 13 vs. the Philadelphia Phillies), 13-inning (May 17 at the St. Louis Cardinals), 15-inning (July 18 vs. the Toronto Blue Jays; Sept. 15 at the Tampa Bay Rays) and 19-inning (Sept. 5 vs. the Blue Jays) marathons.

But if the Red Sox owe their impending division title to success in extras, will that also give them an advantage in the playoffs?

Historically speaking, not necessarily. Since 1900, 22 teams had 10 or more victories and a winning percentage of at least .833 in extra-inning games. Of those, seven -- the 1995 Cleveland Indians (13-0), 2012 Baltimore Orioles (16-2), 1934 Detroit Tigers (12-2), 1961 Yankees (11-2), 1984 Detroit Tigers (11-2), 1981 Oakland A's (10-2) and 2012 Indians (10-2) -- made the playoffs. And of those, only the '61 Yankees and '84 Tigers -- two of the greatest teams in baseball history -- won the World Series.

"I think it shows you're not overwhelmed in [tight] circumstances and you are able to grind out wins," Red Sox president of baseball operations Dave Dombrowski said. "So, I think being exposed to that is helpful. I think it also shows we've got a good bullpen and a deep bullpen. That's good. But I don't know that it guarantees anything."

Indeed, the Red Sox owe their extra-inning prowess primarily to the strength of the bullpen. Through Sunday, Boston relievers combined for a 3.02 ERA, second best in the majors behind the Indians. But after regulation, they have allowed only eight earned runs in 57 2/3 innings for a 1.25 ERA and held opponents to a .185 average (36-for-195) and five extra-base hits.

The bullpen is filled with hard throwers with strikeout ability who don't put many runners on base. It's deep, too, with closer Craig Kimbrel, Matt Barnes, Heath Hembree, Robby Scott, Joe Kelly, Fernando Abad, Blaine Boyer, Brandon Workman and trade-deadline addition Addison Reed each making at least 25 appearances and posting sub-4.00 ERAs.

"It feels like we play extra innings every other game," Barnes said. "We laugh about it. We're going out there and trying to continue to put up zeroes."

A stout bullpen tends to be a difference-maker in the playoffs. Look no further than the Kansas City Royals in 2014-15 and the Indians last year. And the formula of shortening games with dominant relief pitching goes back much further than that. Some of the most important figures in the Yankees' dynasty were Mike Stanton, Jeff Nelson, Ramiro Mendoza, Graeme Lloyd, John Wetteland and, of course, Mariano Rivera.

Dombrowski knows firsthand the pitfalls of a rickety bullpen in October. In all likelihood, his 2013 Tigers would have gone to the World Series if Joaquin Benoit hadn't given up a grand slam to David Ortiz in Game 2 of the AL Championship Series, one example of several bullpen breakdowns that cost Detroit dearly during Dombrowski's tenure.

"We feel very good about our bullpen and the depth of it," Dombrowski said. "Of course, you have to go out and do it that time of year. But they've been through it. These guys have performed well in tight situations in extra-inning games. This is probably as deep as any [bullpen] I've been associated with. Not just deep in numbers, but deep in abilities."

But here's the downside to all those extra-inning games: The bullpen has gotten so many chances to shine because of the offense's tendency to go cold for long stretches.

The Red Sox have hit fewer home runs than any team in the league, relying instead on stringing together hits and walks to score. That can be a difficult way to sustain consistent offense. And the Sox have scored only 32 runs in 59 extra innings over 18 games, a total that includes a seven-run 15th inning Sept. 15 at Tampa Bay.

Among the other teams that have clinched a playoff spot, none has played more than 12 extra-inning games. The Houston Astros have played eight, the Indians only six.

"I think our offense, we'll take our walks and move a runner where some teams may just look to hit a homer or something like that," Red Sox left fielder Andrew Benintendi said. "Just the kind of team we are. We try to get guys on base and move them over and then get them in."

And if that means having to work overtime to win, well, the Red Sox are happy to put in the hours. At least they can say they have played in more than their share of close games, which might steel them for what they're bound to experience in the postseason.

"We're definitely familiar with it," Barnes said. "I don't know it's a good or bad thing. Maybe it helps when you get into the postseason, always playing close games. Hopefully we can get it done in nine more times than not, but if we go extras, everybody is ready for that."