Max Scherzer pitched five innings Thursday against the Rockies. (Katherine Frey/The Washington Post)

Washington Nationals ace Max Scherzer felt some pain when he woke up Friday morning, and an MRI exam revealed a mild strain of the rhomboid muscle below his right shoulder in his upper back. He received a stem cell injection and will be shut down Friday and Saturday. The Nationals then will see whether he can make his next scheduled start, set for Tuesday against the Atlanta Braves.

Scherzer, who turns 35 on Saturday, had been on the injured list with inflammation in the bursa under his right shoulder blade. He returned Thursday and gave up three runs in five innings of an 8-7 loss to the Colorado Rockies. He felt fine after the outing — only mentioning slight pain in his left wrist — but then felt discomfort after a night’s sleep. And it was in the same spot that has given him trouble since a start at the Detroit Tigers on June 30.

“It’s both,” Scherzer said Friday when it was suggested that he didn’t seem too concerned or encouraged. "I’m not happy. But on the other hand, we’re talking minor strain, so there’s a heck of a lot of other things that could be wrong with your body and arm and shoulder. Those are really — knock on wood, those are the bad stuff.

“We’re just digging through this [scapula] injury, and the other good thing is that when I’m on the mound and throwing, I don’t feel any pain. … Every time I play catch, I’m on the mound and throwing every ball at 100 percent.”

Scherzer has received a stem cell shot in the past, that one in his right thumb, and was still able to make his next start. On Friday, he did not predict whether that will be the case this time. This lingering pain has been a conundrum since it flared up after that start in Detroit. It was first diagnosed as a mid-back strain, and the Nationals expressed confidence that Scherzer could avoid the IL altogether. But then that changed to bursitis in his right scapula, and he missed two turns in the rotation.

He is confident that it was a sound decision for him to start Thursday: “I was 100 percent in the bullpen throwing every pitch, 100 percent Tuesday, 100 percent Wednesday," he said. “Letting the ball eat, felt no pain, so every time I’ve been in that situation I take the ball.” The question now is how the Nationals can resolve the issue before it forces Scherzer to miss even more time. Manager Dave Martinez mentioned Friday that Washington will consider the pennant race and potential key September starts as it handles this setback.

The Nationals, after all, go as their perennial Cy Young Award candidate does. Scherzer has a 2.41 ERA and had a career-high seven consecutive winning decisions before Thursday’s no-decision. He had a 1.00 ERA in six June starts, posting 68 strikeouts against five walks.

“I felt like I was back to 100 percent, throwing a bullpen, stepping on everything. We kind of thought we were through this," Scherzer said. "And the fact that it kind of reoccurred, now we got to start thinking: What did we miss? Everybody, myself included, what did we not do to make sure this was completely gone? Nobody is at fault; now we just have to try something maybe a little bit different.”

The stem cell injection is the next attempt, and Scherzer said he doesn’t feel that an altered routine would keep him from pitching Tuesday. This is the pitcher who lobbied to start Sunday in Atlanta, four days ahead of when he actually came off the IL, before Martinez told him to relax. Scherzer is good at many things, but relaxing is not one of them. He would start every day if he could, but he also has been mindful about listening to his body and the training staff throughout the past few weeks. He felt a lot of pain after a start against the Kansas City Royals on July 6, saying he couldn’t even lift his shoulder the next morning. The most recent pain was not that bad — Scherzer said he could lift his shoulder and had range of motion — but he knew something was a bit off.

His usual between-starts routine is to throw a bullpen session three days before his outing. That would require him to throw one Saturday — which he will not be allowed to do — but Scherzer noted that he could move it to the day before he’s scheduled to pitch. That would be a lighter session, probably around 15 pitches, if his health permits. The next few days will dictate whether that becomes the plan.

The Nationals are otherwise thin in their rotation, with Joe Ross already expected to make a spot start against the Los Angeles Dodgers on Saturday. Austin Voth remains on the IL with biceps tendinitis that has crept into his shoulder. Erick Fedde was optioned to Class AA Harrisburg on Thursday, to allow the Nationals to have one game of catcher Raudy Read, and he has to remain in the minors for at least 10 days unless he’s called up for an injured player. Scherzer would qualify as that only if he goes back to the IL.

The Nationals will spend the weekend hoping that doesn’t have to happen. To help an overworked bullpen, they recalled reliever Kyle Barraclough from Harrisburg and sent outfielder Andrew Stevenson back to Class AAA Fresno. That puts the bench at three players and the bullpen at nine arms, and it gives them an unbalanced roster going into a series with the National League’s best team.

But that’s not close to the Nationals’ biggest concern. Scherzer will remain that until this mild strain is resolved.

“He’s aggravated,” Martinez said Friday. "I told him: ‘Let’s just get you right. When you’re right, you’re one of the best. Let’s get it right this time.’ ”

FRIDAY’S LINEUPS

Dodgers (67-37)

Joc Pederson, 1B

Alex Verdugo, LF

Justin Turner, 3B

Cody Bellinger, RF

Max Muncy, 2B

A.J. Pollock, CF

Corey Seager, SS

Russell Martin, C

Hyun-Jin Ryu, P

Nationals (55-47)

Trea Turner, SS

Adam Eaton, RF

Anthony Rendon, 3B

Juan Soto, LF

Howie Kendrick, 1B

Kurt Suzuki, C

Brian Dozier, 2B

Victor Robles, CF

Aníbal Sánchez, P