WASHINGTON >> Never in the long history of Major League Baseball has any team held a lead in September of eight games or more for a postseason berth and failed to clinch.

Got that? Never happened. Not even once.

And yet it could happen twice in 2011, because the Boston Red Sox and Atlanta Braves are teetering on the verge of collapsing in the season’s final month the way no club has before.

Heading into Monday, each team’s once-cushy lead in its respective league’s wild-card standings was down to one game with three to play: Boston barely ahead of the Tampa Bay Rays in the AL; Atlanta hanging on ahead of the St. Louis Cardinals in the NL.

"You don’t want to be against the wall," Red Sox DH David Ortiz said, "because there’s no way to escape."

According to STATS LLC, the 1995 California Angels blew the largest September lead to miss out on the playoffs — 7½ games. Five teams wasted seven-game September leads and didn’t reach the postseason, as long ago as the 1934 New York Giants, and as recently as the 2009 Detroit Tigers, STATS said.

Turn this year’s calendar to the morning of Sept. 6, and the Braves enjoyed a margin of 8½ games in the NL.

Go back to Sept. 4, and the Red Sox began the day owning a nine-game lead for the AL wild card. A handful of days earlier, on Aug. 31, the Red Sox even led their division by 1½ games.

"Obviously, they’re struggling a bit, and that happens. But from our perspective, it’s more important what we do," Rays manager Joe Maddon said. "It’s fortuitous that they’ve had a hard time, but I love the fact that we’re taking care of business."

With all six division titles already locked up as of Friday — not since 1986, when there were only four divisions, had all been sealed so early, STATS found — the wild-card races give fans something to keep an eye on down the stretch.

Boston was in danger of dropping into a tie with Tampa Bay on Sunday, but Jacoby Ellsbury’s three-run homer in the 14th inning helped the Red Sox pull out a 7-4 victory shortly before midnight against the AL East champion New York Yankees in the second game of a day-night doubleheader, salvaging a split.

"It was a BIG win," Red Sox manager Terry Francona said, "but we’ve got to go down tomorrow and play well."

Starting Monday, the Red Sox wrap up the regular season with three games at the last-place Baltimore Orioles, who took three of four at Fenway Park on Sept. 19-21, while the Rays host the Yankees.

"We’ve got to go win every game," Boston closer Jonathan Papelbon said. "That’s the way it is."

Over in the NL, the Braves host the best-in-baseball Philadelphia Phillies, while the Cardinals get to close by taking on the worst-in-the-majors Houston Astros.

"All the pressure’s on St. Louis, because if they don’t win, they can’t go anywhere. Even if we do lose, they have to win," Atlanta rookie first baseman Freddie Freeman said after his team’s 3-0 loss at the Washington Nationals on Sunday. "So that’s how I look at it — and I think how everybody else looks at it, too."

Hmmmmm. Maybe.

The Cardinals decided before their 3-2 comeback victory at the Chicago Cubs on Sunday that they would all wear Hawaiian shirts on their team flight that night. Even manager Tony La Russa was going along with it.

While St. Louis has won 15 of its past 20 games, Atlanta has lost 10 of 15.

"Every missed opportunity in September — it’s big," Braves manager Fredi Gonzalez said.

Similarly, the Red Sox have lost 15 of their past 21 games, and the Rays have closed the gap even though they’re only 14-10 in September.

So what exactly has been going wrong for Boston and Atlanta?

"It’s all of us," Boston’s Ortiz said. "We’re all to blame."

Well, that could be accurate, but to boil it down to the basics: The Red Sox aren’t pitching well or playing solid defense lately, while the Braves are having a hard time hitting.

Boston made three errors Sunday, raising its total to 17 over the past 12 games, and the team’s starters are 4-12 with a 7.16 ERA this month.

Atlanta, meanwhile, managed only four hits, all singles, on Sunday, and its last 15 batters made outs, seven via strikeout. The first four players in the batting order — Michael Bourn, Martin Prado, Chipper Jones and Dan Uggla — combined to go 0 for 16 with five strikeouts against four Nationals pitchers.

Ooooof.

Consider, too, what happened for the Braves when they did give themselves good chances to get on the scoreboard against the Nationals.

In the third inning, they loaded the bases with no outs but came away with nothing.

In the fifth, they had runners on second and third with one out but came away with nothing.

"Since it’s crunch time," Uggla said, "there’s a little bit of added pressure there."

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AP Sports Writer Howie Rumberg in New York contributed to this report.