"He had inflammation in his throwing shoulder, rotator cuff," manager Davey Martinez said. "He's got medication. He's going to take three to four days and then he'll start strengthening again. So hopefully this ain't a real major thing and he'll be starting to throw again maybe by the end of next week. That's what we're shooting for."
Herrera entered the nightcap of Tuesday's doubleheader against the Braves in the ninth inning of a 1-1 game. He allowed hits to three of the four batters he faced, including a two-run triple to Ender Inciarte. Following that at-bat, Herrera, who was charged with a loss in the 3-1 defeat, met on the mound with medical staff and then exited the game with what the team described as right shoulder tightness.
The Nationals recalled right-hander Koda Glover from Triple-A Syracuse to take Herrera's place on the roster.
Herrera, 28, is 1-2 with three saves and a 4.76 ERA in 19 games for Washington, who acquired him from the Royals on June 18. Although he was the closer in Kansas City, the Nationals planned on him serving in a setup capacity. But when All-Star closer Sean Doolittle landed on the disabled list in early July (foot), Herrera slid into the ninth-inning role.
In Herrera's absence, righty Ryan Madson, 37, will serve as Washington's primary closer, according to Martinez.