In his 13th Major League season, Blanton has yielded 14 runs (13 earned) in 12 1/3 innings with an 0-2 record for the Nats.
"He's been trying to pitch through it for awhile now," Nationals general manager Mike Rizzo said. "He went out and threw a bullpen [Tuesday], he felt it and he felt it again today. "Don't forget, he came into Spring Training extremely late. He started up extremely quickly and hasn't been right for awhile. We're going to shut him down for awhile to get the old Blanton back."
Manager Dusty Baker said, "You know Joe is a lot better than he has pitched this year. When you're not 100 percent, when you're not hurt enough to go on the DL, you feel good some days, you feel bad some other days and the mind kind of plays tricks on you. [Pitching coach] Mike Maddux had a bullpen session with him yesterday and you could tell something was wrong."
The left-handed Grace, meanwhile, has allowed three runs in 4 1/3 innings for the Nationals, shuttling between Syracuse and Washington.
Rizzo also discussed Erick Fedde, the Nationals' top pitching prospect, per MLBPipeline.com. A starter at Double-A Harrisburg, Fedde was moved to the bullpen Tuesday and will continue in that role when he joins the Nationals, which is expected to be later this season.
"It's often good to get a Minor League prospect's feet wet in the big leagues out of the bullpen," Rizzo said. "We still view him as an effective starter. ... Start out of the bullpen, we can gradually stretch you out and put you back as a starter any time."
A 24-year-old right-hander, Fedde has a 3.30 ERA at Double-A Harrisburg. Another factor is that Fedde underwent Tommy John surgery in 2014. Two days later, the Nationals made him the 18th pick in the Draft.
"We're still controlling his innings," Rizzo said. "Make sure he can pitch the whole season with us and stay within his pitching parameters as far as innings go. And it addresses a direct need for us in the big leagues."
The Nationals bullpen began play Wednesday with a 5.19 ERA, which ranked 27th in the Majors.