WASHINGTON — The already-shorthanded Nationals pitching staff sustained another setback on Sunday when starting right-hander Stephen Strasburg (right shoulder inflammation) and righty reliever Wander Suero (left oblique strain) were placed on the 10-day injured list. There is no timetable for Strasburg’s return.

The starting rotation has been without southpaw Jon Lester, who is ramping up for his 2021 debut after beginning the season on the IL under COVID-19 protocols. Right-handed late-inning reliever Will Harris also has been sidelined since Spring Training with right hand inflammation. On Saturday, the team announced left-handed reliever Luis Avilán sustained an ulnar collateral ligament (UCL) tear.

“For me, it’s been a crazy start of the year from the beginning,” manager Dave Martinez said Sunday morning. “We’ve got to start looking at some of this stuff and the possibility of some of these things happening. It’s unfortunate, but we’ve got to move on.”

Strasburg was scheduled to make his third start of the season on Sunday. He is 0-1 with a 6.30 ERA in his first two starts this season.

In his most recent outing on Tuesday against St. Louis, Strasburg threw 88 pitches in just four innings. He allowed eight runs off as many hits, issued five walks and struck out three. That night, a TV camera filming in the tunnel behind the Nats dugout showed Strasburg rubbing between his neck and right shoulder, which caused a controversy.

“We talked to him after the game — he said he felt fine,” Martinez said. “He went through his regular routine this whole week. After his bullpen, which he threw well, he said he didn’t feel right. So that was an indication that we needed to get him checked out.”

The 32-year-old was limited to five frames last year because of carpal tunnel neuritis in his right hand. He reported to Spring Training healthy after undergoing surgery last August. This year, though, his average fastball velocity has dropped to 92.1 mph — down from 93.9 mph in 2019, his last complete season.

“I don’t want him out there thinking about his mechanics, thinking about his shoulder,” Martinez said. “We want him to go out there feeling good about himself, because when he does that, you’ve seen what he can do for us. This is all about Stephen right now and taking care of Stephen to make sure that when he does come back, he’s ready to go.”

Veteran right-hander Paolo Espino was tabbed to take the mound against Arizona in place of Strasburg. The 34-year-old has made three Major League starts over his career, most recently on Sept. 22, 2020, against the Phillies. Espino had built up to 85 pitches at the alternate training site in Fredericksburg, Va., before being informed Saturday morning he could be called up to start.

Martinez said the Nationals considered Austin Voth — who filled the fifth starter role last season — to start Sunday, but he had pitched back-to-back days this week.

Suero exited Saturday’s win over Arizona after he grabbed his left side following his 11th pitch. An MRI following the game revealed an oblique strain. The consistent reliever has thrown 6 1/3 innings while allowing just one run in eight appearances this season.

“He said he doesn’t feel that bad,” Martinez said. “Typically, when you can’t breathe, it’s a severe strain. He said he’s breathing fine with no pain. Hopefully, with this stint on the IL and building him back up, we’ll get him back as soon as possible. It’s weird how these obliques are — you just never know. So we’ve got to make sure that he’s completely healthy.”

The Nats recalled right-hander Ryne Harper from the alternate training site in a corresponding move. He threw 23 2/3 innings out of the ‘pen for Washington last season.