The Nationals’ fifth-starter carousel is going to be without one of its members for a while.

Austin Voth, who was beginning to establish himself as a viable back-of-the-rotation option for manager Davey Martinez before landing on the injured list earlier this week, has been diagnosed with shoulder tendinitis and has been shut down from throwing.

Voth was tentatively scheduled to start last Sunday in Atlanta, taking over with Max Scherzer not yet ready to return from his own injury. But the rookie right-hander reported shoulder pain after throwing off a bullpen mound between starts, and was scratched from the start.

The Nationals placed Voth on the 10-day IL with what initially was called right biceps tendinitis. He planned to try throwing again Tuesday at Nationals Park but continued to feel discomfort and thus was scheduled to undergo an MRI. That MRI revealed tendinitis in the shoulder, so the Nationals decided not to take any chances and shut him down for now.

“Yesterday he said he felt better,” manager Davey Martinez said. “But we’re going to make sure we’re very careful with him.”

Voth was 1-0 with a 4.35 ERA in four starts, essentially sharing the No. 5 starter’s job with Erick Fedde, who is 1-1 with a 3.40 ERA in 13 games (eight starts). Fedde, who pitched the first end of Wednesday’s doubleheader against the Rockies, was optioned to Double-A Harrisburg after the game because the club won’t need that fifth starter again until Aug. 6.

The Nationals do need a fill-in starter for Saturday’s game against the Dodgers. They are still listing that starter as “TBA” - Aníbal Sánchez starts Friday’s series opener, with Stephen Strasburg in Sunday’s finale - but the only viable option on the current 25-man roster is Joe Ross. Ross, who gave up three runs in 5 1/3 innings against the Braves on Sunday as the replacement for Voth, is on full rest and remains on the active roster.

In other news, the Nationals optioned catcher Raudy Read back to Triple-A Fresno before tonight’s game, opening up a roster spot for Scherzer, who makes his return from injury to face the Rockies. Read wound up spending only one day in Washington, pinch-hitting during Wednesday’s doubleheader nightcap.