Pitching, defense to blame for Red Sox’ downturn and up for analysis after an ugly month of August

The Astros cut out the lights at Fenway Park when they swept the Red Sox this week, spoiling any chance at a postseason run.

In truth, though, the Red Sox were doomed well before that. It comes down to pitching and defense.

The Red Sox banked on pitchers Chris Sale, Tanner Houck, and Garrett Whitlock to get them through the August storm. In translation, it was up to guys returning from injury who had spent much of the summer on the injured list. After covering much of July with bullpen games in two rotation spots, Sale and Houck were supposed to help amplify the rotation despite the pair’s pitch-count limit. Whitlock, meanwhile, was supposed to amplify a bullpen that looked like it was establishing itself as one of the best in the big leagues.

But the Sox had other issues before their returns. James Paxton began to fade, posting a 4.81 ERA in his first five starts following the All-Star break. You began to see Brayan Bello show some fatigue, too, when he came out of the break with a 5.34 ERA over five starts. Yet Sale and Houck were better options than running out Chris Murphy as the bulk guy every five days, or even Nick Pivetta, who thrived in that role. The collateral damage to Pivetta’s success was a spent bullpen.

Turns out, the returns of Sale and Houck were more of a hindrance given their limitations and underperformance. Sale was reinstated from the injured list Aug. 11 and Houck returned Aug. 22. Since Aug. 11, the Sox starters have posted a 5.11 ERA while throwing just 88 innings in 19 games and averaging just under 4⅔ innings.

“It’s very difficult,” said manager Alex Cora of finding a way to win while also considering a pitcher’s health. “It’s a balancing act. But at the same time, we’re in the business of winning. When you’re in that chair, and have those 26 guys and everybody in the organization, we’re in the business of winning. But at the same time, you’re not going to jeopardize somebody’s career because we have to win today. That’s for later on in the year. Late September and in October. [At that time] everybody goes in spikes on and we go.

“But right now, at this point, it’s very hard to push Chris to 110 pitches. It’s hard to push Houck to 100 pitches against the Dodgers.”

Whitlock, meanwhile, has been a shell of himself since returning Aug. 13, tallying a 6.75 ERA with opponents hitting .326 against him. The bullpen began to show fatigue, too, yielding a whopping 6.14 ERA for August.

As for the defense, it, by far, is the most concerning part of not just the Red Sox’ current issues, but their future issues.

The Sox have committed the most errors in the game (92). The club ranked 26th in the majors in defensive runs saved as of Thursday (minus-17).

Rafael Devers has taken a step back defensively, and though Cora has backed his third baseman, saying that he is confident Devers can stay at the position, it’s fair to question that assessment. Having to question that, considering the Sox committed $300 million to Devers, should cause some uneasiness within the Red Sox crowd.

Masataka Yoshida is a below-average defender in left field, too. Triston Casas is a below-average defender at first base, but could improve considering he’s just 23. Yoshida, meanwhile, is 30, and likely is who he is in left.

While Yoshida profiles more as a designated hitter, he has only 13 homers in his first big league season. He’s an Alex Verdugo at the plate with a little bit more power, yet lacks the right fielder’s defensive skills. That’s a problem.

The Sox are locked into the trio of Devers, Yoshida, and Casas for at least the next four years, and if primary DH Justin Turner re-signs with the club (he has an option for next year that he certainly will decline considering his offensive production), what do they do to improve defensively? Having a full year of Trevor Story will help at shortstop, but running out three below-average defenders will likely negate Story’s presence.

“We are where we are because we have struggled in certain areas of the game,” Cora said. “And it’s catching up to us.”

Defense, even more than pitching, has determined the Sox’ fate.

Roster expansion includes Valdez, Walter

On Friday, major league rosters can expand to 28 players, with a maximum of 14 pitchers. Infielder Enmanuel Valdez and lefthander Brandon Walter will be the club’s September call-ups from Triple A Worcester and will join the team in Kansas City for a three-game series against the Royals. Outfielder Wilyer Abreu was reinstated from the paternity list and center fielder/shortstop Ceddanne Rafaela will remain on the roster, but infielder David Hamilton was optioned to Worcester . . . The Sox’ rotation for this weekend is as follows: Paxton, Houck, Sale. Kansas City will send Jordan Lyles to the mound for the series opener, then TBD for Saturday, and Zack Greinke for Sunday.

Julian McWilliams can be reached at julian.mcwilliams@globe.com. Follow him @byJulianMack.