The Red Sox acknowledge that they are feeling the weight of their September collapse. (AP)

NEW YORK — A possibility that once seemed unthinkable is now staring the Red Sox in the face. With Boston’s 6-2 loss in Game 1 of its doubleheader against the Yankees, and the Rays having beaten the Blue Jays on Sunday, the Sox’ lead over the Rays in the AL wild card race is now down to one-half game.

And that, in turn, means that what had seemed a preordained ticket to the postseason may vanish tonight. If the Sox lose tonight’s contest against the Yankees, they will find themselves in a tie with Tampa Bay in the wild card race, marking the first time since late June that they have not been in control of their own destiny in the postseason race.

“We know. Everybody here knows,” Sox DH David Ortiz said when informed of that scenario. “We’ve lost, what, 18 games this month? That’s deep. … We’re against the ropes right now. This is not 2 and a half [games in the standings], you know? That game tonight can tell you a lot.”

The frustration has mounted considerably inside the Red Sox clubhouse, with the string of defeats — and the consequent postgame silence that comes from the absence of the music that plays after victories — assuming a somewhat oppressive air. There is now a weight that can be felt.

“We’ve been not playing well for three weeks. It’s not a good feeling,” said second baseman Dustin Pedroia. “You’ve got a pit in your stomach. It’s not fun.

“Losing’s contagious,” Pedroia added. “So is winning. When we started out 2-10, we didn’t play well, and it changes your attitude, your mindset and everything. But when we were the best team in baseball for four months, everyone’s a little bit taller except me.”

There is no magic formula to turn around the Sox’ month-long woes. The natural tendency — and sometimes desire — by outsiders is to see evident distress and outward signs of anger at the state of affairs.

But Ortiz suggested that emotional outbursts are pointless.

“What’s that going to solve? Is that what you do at home when you get mad? It’s not all about being mad or wanting to kill somebody or anything like that,” he said. “It’s about pulling yourself together and all the energy you can waste getting mad, and flipping tables and the other stuff, waste it out there. That’s what I do.”

Indeed, the team feels that a turnaround will come only from a renewed intensity of focus that will improve the team’s execution. Sloppy execution and distracted play have been hallmarks of the team’s September collapse. A reversal is needed if the Sox are to try to hold on to a spot in the postseason.

“We’ve got to stop worrying about what’s happened the last three weeks and come out and play tonight and play hard the rest of the way,” said Pedroia. “What do we have? What’s our lead? We have a half-game lead? Good. Keep playing, man. That’s it. You can’t sit back and say, ‘we’ve got to do this, we’ve got to do that.’ Our leadoff hitter has to get on base. That’s how we have to play, pitch by pitch, man, because you can’t come out of stuff like this trying to do stuff. You try to do things, that doesn’t happen.”

As much as the losses have been disconcerting for the Sox, the style of play that has yielded them has been perhaps even more alarming. The Sox have displayed numerous lapses in their fundamentals, both in the field and on the bases, a development for which manager Terry Francona said that he is accountable.

“I get concerned with everything,” said Francona. “That part falls directly on my shoulders. When it doesn’t go right, it’s my responsibility.”

Yet while the manager pronounced himself accountable for his team’s struggles — at a time when speculation about his job security has suddenly become a hot topic — he also emphasized that, with the season not yet concluded, there is time for his team to reverse its September spiral.

“We have four games. We can write our [destiny],” said Francona. “We just need to work on our writing skills a little bit.”