ST. PETERSBURG -- The slide the Red Sox have been on since coming back from the All-Star break finally brought them below .500 with Tuesday night’s 8-3 loss to the Rays at Tropicana Field while further dimming their postseason hopes.

Now at 75-76, Boston sits under .500 for the first time since June 11. With 11 games left in the season, the Sox are five games behind the Twins for the final American League Wild Card spot.

“It sucks,” said Red Sox manager Alex Cora. “We’ve got three ways [we can be]: average, below average, or above average, right? And right now we're below average. Like I've been saying all along, it’s not lack of effort. It's just not happening for us right now. It was just a bad one tonight.”

Reality is starting to set in for a team that has been hanging around the fringes of contention for several weeks, but is now running out of time.

“It’s tough to say, and it’s coming down to the wire, but it feels like we’ve got to run the table at this point,” said first baseman Triston Casas. “It's been a tough [second half], but that's not to say that we can't finish strong on a high note and win these last however many games and see where it puts us.”

Each time a new series starts, Boston hopes it will be the one to start a surge of wins that has been elusive for months.

Tuesday night started in promising fashion, as Casas hit his first home run since Aug. 25, mashing a two-run shot to right that snapped a scoreless tie in the second inning.

From that point on, the Rays outscored the Red Sox, 8-1.

Nick Pivetta, who was strong early, gave up a solo homer to Junior Caminero on an 0-2 pitch that was high and out of the strike zone in the fourth. From there, the momentum turned to Tampa Bay for the rest of the night.

Caminero, one of the league’s most promising young players, did something that left Pivetta without much to do but tip his cap.

“Yeah, of course,” said Pivetta. “I don’t know. Whatever he did, he did.”

The fifth inning, when the Rays scored four runs on three homers -- two of them off Pivetta -- is the one that really stung.

Pivetta misfired a 2-2 fastball that caught too much of the plate, and Josh Lowe took it out of the park to tie the game. A couple of batters later, Cora came out to check on Pivetta, who felt some cramping in his trap area. The righty stayed in the game for a brief time after that, but it didn’t go well. Jose Siri turned on an outside sweeper and hit it down the left-field line for a homer that put Tampa Bay up for good.

“On the two later home runs, I just didn't execute those pitches at all,” said Pivetta. “They put good swings on them.”

After Yandy Díaz hit a double, Pivetta came out.

“He was cramping. He had a cramp in the trap area. I wanted to make sure he was OK,” said Cora. “I gave him two hitters, and then after that, for me, it doesn't make sense. You have to take care of the players. That's my job, too. So we went to [Bailey] Horn against a lefty. It just didn’t work out.”

Brandon Lowe made it 5-2 when he belted a two-run shot to greet Horn.

A pinch-hit homer by Romy Gonzalez brought the game within two in the eighth, but a bases-clearing double by Siri against Josh Winckowski that just snuck under the glove of a diving Tyler O’Neill served as the final blow.

Winckowski was just one pitch away from escaping a bases-loaded, nobody-out jam with no runs across.

“It's extremely frustrating,” said Winckowski. “When you’re this close to the end of the season, you don't have time to fix it. Damage is done. I feel like we were executing really well. And I don't know how hard he hit it, but it was not a legit hit.”

Legit or not, the 65.6 mph double fell, giving the Red Sox a sinking feeling as they were on their way to a loss that dropped them to 5-10 in September.