“It makes me angry that people say these things because I’ve busted my [butt] to be the best manager I can be,’’ Francona said. “I wasn’t terribly successful this year, but I worked harder and spent more time at the ballpark this year than I ever did.’’

Francona spent the season living in a hotel after he moved out of the Brookline home he shared with Jacque, his wife of nearly 30 years. But he adamantly denied his marital problems affected his job performance.

By numerous accounts, manager Terry Francona lost his ability to prevent some of the lax behavior that characterized the collapse. Team sources said Francona, who has acknowledged losing influence with some former team leaders, appeared distracted during the season by issues related to his troubled marriage and to his health.

“I just know that playing in Boston, you’re required to play your tail off every day to try to win ballgames for this city,’’ Pedroia said. “That’s what hurt so much as a player, that we not only let each other down in the clubhouse but we let the city down.’’

Second baseman Dustin Pedroia, portrayed on a Sports Illustrated cover in August as “the heart of the Red Sox,’’ declined to hold any individual culpable.

This article is based on a series of interviews the Globe conducted with individuals familiar with the Sox operation at all levels. Most requested anonymity out of concern for their jobs or potential damage to their relationships in the organization. Others refused to comment or did not respond to interview requests.

How a team that was on pace in late August to win 100 games and contend for its third World Series title in seven years self-destructed is a story of disunity, disloyalty, and dysfunction like few others in franchise history.

The story of Boston’s lost September unfolds in part as an indictment of the three prized starters. But the epic flop of 2011 had many faces: a lame-duck manager, coping with personal issues, whose team partly tuned him out; stars who failed to lead; players who turned lackluster and self-interested; a general manager responsible for fruitless roster decisions; owners who approved unrewarding free agent spending and missed some warning signs that their $161 million club was deteriorating.

Instead, Boston’s three elite starters went soft, their pitching as anemic as their work ethic. The indifference of Beckett, Lester, and Lackey in a time of crisis can be seen in what team sources say became their habit of drinking beer, eating fast-food fried chicken, and playing video games in the clubhouse during games while their teammates tried to salvage a once-promising season.

With their team in peril and their manager losing his authority, three Red Sox pitchers last month were uniquely positioned to prevent the greatest September collapse in major league history. All the Sox needed was Josh Beckett, Jon Lester, and John Lackey to apply the skills and commitment that previously made them World Series champions.

Sox owners soon suspected the team’s poor play was related to lingering resentment over the scheduling dispute, sources said. The owners responded by giving all the players $300 headphones and inviting them to enjoy a players-only night on principal owner John W. Henry’s yacht after they returned from a road trip Sept. 11.

As it turned out, the Sox swept the Saturday doubleheader, but that stormy day marked the beginning of the end for the 2011 team. It was the last time the team would win two games in a row. After getting two days off, the Sox spent the rest of the season playing uninspired, subpar baseball, losing 21 of their final 29 games.

But numerous Sox players angrily protested. They returned early that Friday from Texas after a demanding stretch in which they had played 14 of 17 games on the road, with additional stops in Minneapolis, Seattle, and Kansas City. The players accused management of caring more about making money than winning, which marked the first time the team’s top executives sensed serious trouble brewing in the clubhouse.

As Hurricane Irene barreled toward Boston in late August, management proposed moving up the Sunday finale of a weekend series against Oakland so the teams could play a day-night doubleheader either Friday, Aug. 26, or Saturday, Aug. 27. The reasoning seemed sound: the teams would avoid a Sunday rainout and the dilemma of finding a mutual makeup date for teams separated by 2,700 miles.

Commitment lacking By all accounts, the 2011 Sox perished from a rash of relatively small indignities. For every player committed to the team’s conditioning program, there was a slacker. For every Sox regular who rose early on the road to take optional batting practice, there were others who never bothered. For every player who dedicated himself to the quest for a championship, there were too many distracted by petty personal issues.

“I went and saw the proper people and it was not an issue,’’ Francona said. “It never became an issue, and anybody who knew what was going on knows that.’’

Francona acknowledged that he consulted the team’s internist, Dr. Larry Ronan, during spring training after one of his children expressed concern about a pill bottle in his hotel room. Francona said the doctor told him he did not have a drug abuse problem. Ronan could not be reached.

Team sources also expressed concern that Francona’s performance may have been affected by his use of pain medication, which he also vehemently denied. Francona said he has taken pain medicine for many years, particularly after multiple knee surgeries. He said he used painkillers after knee surgery last October and used them during the season to relieve the discomfort of doctors draining blood from his knee at least five times.

Growing ineffectiveness Francona, who mutually parted with the Sox after the season, has been careful not to criticize individual players. He generally downplayed the pitchers’ drinking in the clubhouse, but he left little doubt that their absence from the dugout reflected a lack of dedication to the team.

“I think the fans deserve an opportunity to watch me chase that record,’’ Wakefield told Fox Sports, raising eyebrows on Yawkey Way.

Wakefield also was part of the problem. Amid a seemingly interminable quest for his 200th career victory, he went 1-2 with a 5.25 ERA in September, taxing the bullpen as the Sox lost four of his five starts. The 45-year-old knuckleballer then appeared more interested in himself than the team when he asserted in the final days of the season that the Sox should bring him back in 2012 to pursue the franchise’s all-time record for wins (shared by Roger Clemens and Cy Young at 192).

For Beckett, Lester, and Lackey, the consequences were apparent as their body fat appeared to increase and pitching skills eroded. When the team needed them in September, they posted a combined 2-7 record with a 6.45 earned run average, the Sox losing 11 of their 15 starts.

“It’ s hard for a guy making $80,000 to tell a $15 million pitcher he needs to get off his butt and do some work,’’ one source said.

Sources said Beckett, Lester, and Lackey, who were joined at times by Buchholz, began the practice late in 2010. The pitchers not only continued the routine this year, sources said, but they joined a number of teammates in cutting back on their exercise regimens despite appeals from the team’s strength and conditioning coach Dave Page.

Drinking beer in the Sox clubhouse is permissible. So is ordering take-out chicken and biscuits. Playing video games on one of the clubhouse’s flat-screen televisions is OK, too. But for the Sox pitching trio to do all three during games, rather than show solidarity with their teammates in the dugout, violated an unwritten rule that players support each other, especially in times of crisis.

While the seeds of failure were sown long before the shame of September, other foreboding signs emerged earlier. In springtime, there proved to be regrettable irony in the entire starting rotation - Beckett, Lackey, Lester, Tim Wakefield, and Clay Buchholz - donning Sox uniforms and hamming it up in front of the Green Monster for a video of a country music ditty, “Hell Yeah, I Like Beer.’’

But the gestures made no difference. The hapless Sox became the laughingstocks of baseball as they went from holding a two-game divisional lead over the Yankees after the Aug. 27 doubleheader - and a nine-game advantage in the wild-card race over the Rays - to finishing a humiliating third in the AL East.

Beckett, Lackey, and Lester did not reply to messages left on their phones and with their agents.

“The guys that weren’t down on the bench, I wanted them down on the bench,’’ Francona said last week in a contractual appearance on WEEI. “I wanted them to support their teammates.’’

But Francona’s troubles ran deeper than the three starters. As he completed his eighth year as manager - a historic run in which he guided the Sox to two World Series titles - Francona by his own admission grew less capable of motivating the team. His losing influence with some former leaders came into sharper relief after he convened a closed-door meeting Sept. 7 after a 14-0 victory the previous night to address the clubhouse malaise. His players responded by failing to adjust their attitudes or improve their slipshod performances.

In the face of his team’s corroded spirit, Francona became increasingly ineffectual, according to team sources. Francona was burdened not only by the frustration of coping with the least dedicated group of players of his Boston tenure, but by the likelihood that Sox owners would not exercise his contractual option for 2012.

Francona took strong exception to the suggestion that his problems motivating the players had anything to do with his commitment to the team.

“You never heard any of these complaints when we were going 80-41 [from April 15 to Aug. 27] because there was nothing there,’’ Francona said. “But we absolutely stunk in the last month, so now we have to deal with a lot of this stuff because expectations were so high.’’

While Francona coped with his marital and health issues, he also worried privately about the safety of his son, Nick, and son-in-law, Michael Rice, both of whom are Marine officers serving in Afghanistan.

In the end, only Pedroia and a few other players appeared to remain fully committed to winning, according to team sources. They said the veterans who no longer actively exerted their leadership included the captain, Jason Varitek, who was saddled with injuries and ineffective on the field (he batted .077 in September).

The 39-year-old catcher, in a brief conversation, chastised a reporter for calling him at home and otherwise declined to comment.

Other than Varitek and Wakefield, the only holdovers from Francona’s 2004 championship run were David Ortiz and Kevin Youkilis. Although Ortiz once gathered his teammates in September to try to rally them, his most memorable act off the field in 2011 was bursting into a Francona news conference to profanely complain about a scorer’s decision that could have cost him credit for batting in a run.