By Michael Hurley, CBS Boston

BOSTON (CBS) — The Texas Rangers entered this week’s series vs. the Red Sox as one of the worst teams in baseball.

So what, exactly, does that make the Boston Red Sox?

Yes, they eventually won on Monday afternoon, with Travis Shaw clubbing a grand slam in the bottom of the 11th inning. But that win came against one of the worst teams in MLB, and it was a whirlwind getting there … thanks in large part to Matt Barnes.

When Barnes trotted to the mound with a two-run lead in the ninth inning on Monday afternoon, he and the Red Sox were poised to salvage a series win over the Rangers, recovering from Saturday’s embarrassing defeat and coming away with a series win over Texas.

That ninth inning, though, did not go particularly well for the home team.

Barnes allowed a hard-hit infield single to Nathaniel Lowe. It happens.

Barnes then allowed a clean single through the right side by DJ Peters to put two on with nobody out. Not ideal.

Barnes got Jason Martin to chase strike three to get the first out of the inning. Then he induced a near-double play ball that could have ended the game.

It did not.

Xander Bogaerts made a diving stop behind the second base bag, but his flip to Christian Arroyo didn’t connect, as Arroyo was eager to make a barehanded snare before firing to first place for the game-ending double play.

So, with the bases loaded and one out, Barnes had some work to do. He didn’t do it. Instead, Barnes served up a heater over the heart of the plate, and Andy Ibanez drove it deep into right field for a ground rule double. Had it stayed in the park, it likely would have plated the go-ahead run from first base. Instead, it merely scored two runs, tying the game at 3-3.

At that point, Barnes had to exit the game. Garrett Whitlock came on and struck out Jose Trevino before hitting Yonny Hernandez to load the bases. He ended the frame, though, by getting Isiah Kiner-Falefa to strike out.

Whitlock would go on to save the day — as much as it could be saved. He ended up allowing one hit and striking out four batters in 2.2 innings of work after relieving the closer.

And it’s the closer who will certainly be the focus after this one. While some bad luck was involved, Barnes’ final line was ugly: 0.1 IP, 4 H, 2 ER. And that’s a continuation of what has been a grisly stretch for the All-Star closer. He’s now allowed nine runs — all earned — in his last 4.1 innings pitched across his most recent seven outings.

For comparison, Barnes allowed just 11 earned runs from Opening Day through Aug. 4. He’s now allowed nine earned runs since Aug. 7.

His ERA from April through July was 2.30. His ERA in August is now 15.19. He has more losses (3) and blown saves (2) than saves (1) this month.

It is, certifiably, an issue.

Manager Alex Cora said last week that he’d need to give Barnes proper rest, especially after using him in both ends of a double-header vs. Tampa. And while his previous two innings — both on four days of rest — went well enough, Monday’s outing with two days of rest was a problem.

As far as the Red Sox are concerned, the most recent outing was salvaged. The Red Sox managed to eke out a second win in the three-game series with the Rangers, who entered the series with a 42-79 record. They’re still in position for a wild card, and they figure to remain there for at least the balance of the week, with the 54-70 Twins coming to Fenway on Tuesday.

But in the back end of the bullpen, they’ve got an issue. Perhaps it’s a case of Barnes coming back to earth after an otherworldly start to the season. Perhaps — more likely — it’s a matter of fatigue, as the physical stress of the closer role may be taking a toll on the 31-year-old.

Whatever it may be, the Red Sox will need a resolution quickly. With their season hanging by a thread, they can’t afford to kick away many more winnable games. They’re now 8-16 in their last 22 games. Three of those wins have come against the worst team in baseball. Two have come against the third-worst squad, and one of those came only after a blown save in the ninth, a comeback in the 10th, and a walk-off in the 11th.

Getting Barnes back to his first half self — or at least reasonably close to it — may not be the only thing the Red Sox need to do in order to keep their playoff hopes alive. But it certainly ranks near the top of the list.