After Saturday's game, Glover, who was named the Nats' closer May 25, said he aggravated a back injury Saturday morning while reaching down for body wash in the shower. The right-hander didn't tell the coaching staff until after his outing, and he said the injury worsened by pitching Saturday.
"It doesn't make it any easier," Nationals manager Dusty Baker said of losing Glover. "It hadn't been easy so far. Why expect it to be easy now? It's been very difficult. We have to do what we have to do, mix and match and hope the guys we bring in do the job."
Saturday was Glover's first blown save after he secured eight saves.
To replace Glover, the Nats could give Blake Treinen or Shawn Kelley another chance after they both lost the role earlier this season, but they have respective ERAs of 6.33 and 7.47. Matt Albers has the team's best ERA (1.08) and has been used mostly as a setup man, though he has notched two saves.
Blanton had been on the DL since May 17 with right shoulder inflammation. The right-hander has a 4.38 career ERA, but he struggled in 14 appearances to start the season, pitching to a 9.49 ERA and giving up six home runs. Blanton pitched one inning with Double-A Harrisburg on Thursday, not allowing a hit and striking out two. He made his first big league appearance since May 13 on Sunday, tossing a scoreless ninth, though the Nationals trailed, 5-1, when he entered.
Blanton said his throws had weak finishes before, particularly his fastball and slider, his two main pitches. He said adjusting his arm slot helped accelerate the ball.
"The last couple two or three times I threw, it was more normal than it had been in awhile, mechanically speaking," Blanton said. "As soon as I came back to throwing, I felt good and I felt like I wouldn't have a relapse. I was able to freely try to work on mechanics."
Blanton is confident he can return to being a late-inning option for the bullpen, which entered Sunday with the fifth-worst ERA in the Major Leagues.
Kyle Melnick is a reporter for MLB.com based in Washington.