WASHINGTON -- Max Scherzer felt optimistic after exiting Friday’s start against the Giants having thrown just 12 pitches. His early departure was caused by a tweak in his groin, and an MRI showed there was inflammation but no muscle strain.

“It’s really best-case scenario in terms of what the injury is and that I’m really day to day, and that this could subside pretty quickly here,” Scherzer said after the Nats’ 1-0 loss.

Washington's ace right-hander retired San Francisco leadoff batter LaMonte Wade Jr. on a fly ball to left field and had a 3-2 count on Brandon Belt when he started stretching on the mound.

“I threw a pitch there to Brandon Belt and all of a sudden, I felt my groin tweak on me,” Scherzer said. “When I had that happen -- it’s foreign for me to have that type of injury on that location of my body. [I] knew I needed to take a warmup pitch -- I couldn’t look at myself straight if I didn’t throw another warmup pitch. … It just wasn’t an injury that you could pitch through.”

Scherzer has been the anchor of the Nats’ shorthanded starting rotation. He entered Friday’s game with a 2.22 ERA and a 5-4 record over 12 starts, notably posting a 1.72 ERA in his last seven outings. Scherzer became the first National League pitcher to record 100 strikeouts this season, including 10-plus in three of his starts. He doesn’t expect to miss much time before getting back in action and will be reevaluated on Saturday.

“I was pretty confident that this was very mild,” Scherzer said. “I could feel it on one pitch, and that’s where I knew I didn’t blow through it. … Going into the clubhouse, I was frustrated as all get out, but there was nothing I could do about it. I wasn’t worried really beyond that this was just a little grab, and it turns out that’s what it was.”

Scherzer was replaced by righty Paolo Espino, a multiple-innings reliever who started one game this season. Taking the mound on short notice, Espino threw an efficient 3 1/3 innings with a career-high five strikeouts, three hits and one run -- a homer to Buster Posey -- off 50 pitches (35 strikes).

“When they took me out of the game and everybody was standing up and clapping and making noise, it was a very emotional and exciting moment,” Espino said, adding: “[I felt] happiness, feeling like people actually [were] liking and loving what I did tonight. That was really nice.”

From there, Kyle McGowin, Wander Suero, Ryne Harper and Sam Clay combined to throw 5 1/3 scoreless frames.

Scherzer said with a smile that he will owe the bullpen a big dinner on the road to show his appreciation. The Nats’ offense did not capitalize on the relievers’ limiting the Giants’ bats, though, and they didn’t plate a run for the eighth time this season.

“I can’t say enough of what they did,” Martinez said of the bullpen. “They were outstanding, they really were. What a job they did. I was pulling for us to get just two runs, because they held it together.”

The Nationals have been battling health issues on the mound throughout the season. Scherzer has been a reliable arm to spell relief for the frequently called-upon bullpen, an anticipated benefit ahead of Saturday’s split doubleheader. Erick Fedde is slated to return from the COVID-19 IL on Saturday to start one of the games. He has not appeared in a Major League contest since May 16.

No. 2 starter Stephen Strasburg is sidelined on the injured list with a neck strain, and there is no timetable for his return as he battles nerve irritation. Reliever Austin Voth also is on the 10-day IL after he sustained a broken nose on Sunday against the Phillies while opening a bullpen game. Late-inning reliever Will Harris is out indefinitely due to thoracic outlet syndrome in his throwing arm.