OAKLAND, Calif. — The Royals could be without embattled reliever Joakim Soria for at least 10 days after soreness in a lower-back muscle prompted an MRI on Thursday.

The extent of the injury likely will not be known until today. The expected absence of Soria, however, does lead to another question: What will the bridge to closer Kelvin Herrera look like now?

For now, Royals manager Ned Yost has indicated that right-hander Brandon Maurer could be in line for more duty in the eighth inning.

“I think Maurer is gonna do it,” Yost said on Wednesday. “It’s just been a little (like) getting his feet underneath him a little bit.”

The comments came just an hour or so after Maurer blew a 6-4 lead in the bottom of the eighth inning, surrendering a two-run blast to Oakland’s Matt Chapman. The Royals rallied to win 7-6 on the final day of an eight-game road trip. The appearance marked the latest shaky outing for Maurer since being acquired from the San Diego Padres in a six-player trade in late July.

Maurer has yielded eight earned runs and 15 hits in 8 2/3 innings across 10 appearances. He’s struck out 10 batters while issuing six walks. The performance comes after Maurer posted a 5.72 ERA in 39 1/3 innings while serving as the Padres’ closer. He converted 20 saves in 23 opportunities.

Yost said the Royals still believe in Maurer’s power stuff, which includes a fastball that averages 96.6 mph and a slider that he throws more than 29 percent of the time. In recent days, Yost added, pitching coach Dave Eiland has identified some flaws in his delivery.

“Dave is making a couple little mechanical tweaks with him,” Yost said. “But (the) stuff is really good. In essence, he made one bad pitch.”

The Royals will open a three-game series with the first-place Cleveland Indians on Friday night. And the potential elevation of Maurer into important situations serves to reveal, in part, why the Royals continued to use Soria in high-leverage spots, despite a slew of blown saves and inconsistency.

After leading baseball with a 2.00 ERA in July, the Royals’ bullpen has posted a 6.75 ERA in August, second-worst behind the Padres. Reliever Kelvin Herrera is the only member of the current group with an ERA under 5.00 since the start of the month.

The numbers include an unsightly 10.38 ERA from Soria after he allowed four runs in a meltdown on Tuesday. Yet they also include regression from Mike Minor (6.43 ERA in seven innings), Peter Moylan (6.00 ERA in six innings) and Scott Alexander (5.40 ERA in 8 1/3 innings). In addition, left-hander Ryan Buchter, who was also acquired from the Padres, has posted a 5.14 ERA in seven innings in August.

The struggles could be explained, in part, by fatigue. The poor numbers dovetail with a slew of short outings by the club’s starting pitchers.

Yet for now, Yost appears set to offer Maurer more outings in the eighth, while mixing and matching with Moylan, a right-handed specialist, and Alexander, a lefty sinkerballer, in the sixth and seventh innings.