WASHINGTON -- The Nationals placed reliever Justin Miller on the injured list with a strained right rotator cuff prior to Saturday night’s game against the Cubs. Tanner Rainey, who was acquired from the Reds this offseason in exchange for Tanner Roark, has been called up to take his place and perhaps provide some new life to a beleaguered Nationals bullpen.

Rainey joins the Nationals for his first stint of the season. He had been on a roll with Triple-A Fresno, not allowing an earned run in seven straight appearances (7 2/3 innings) with 18 strikeouts and just one walk. Opponents batted just .148 against him during that span. In 16 appearances overall in Triple-A, he struck out 16.0 batters per nine innings but has also walked batters at an alarming rate (6.0 per nine innings).

“He’s been pitching well,” manager Dave Martinez said. “And he’s here to help us in the bullpen. … He’s got a live fastball, his slider towards the end of Spring Training was really, really good.”

Rainey, 26, had a brief Major League stint with the Reds last season, and it did not go well -- 19 earned runs in seven innings (24.43 ERA) with seven strikeouts and 12 walks. However, he throws a fastball that sits in the upper 90s and can touch triple digits with the ability to induce swing-and-misses -- something this scuffling Nationals bullpen, which began the day with a Major League-worst 6.82 ERA, is short on.

Miller felt discomfort in his rotator cuff in the seventh inning of Friday’s 14-6 loss to Chicago and lands on the injured list for the second time this season. He is one of the few Nats relievers who has enjoyed stretches of success on the mound -- he had eight consecutive scoreless outings before giving up a two-run homer -- and overall owns a 4.02 ERA in 17 games this season with a strikeout-to-walk ratio of 11-to-4.

Robles day to day

Victor Robles was out of the Nationals' lineup Saturday, his left wrist still sore one night after getting hit by a pitch from Cole Hamels. Martinez was hopeful Robles would be available to pinch-hit late in the game, if needed, but that seems unlikely after Robles felt discomfort when trying to take swings before the game.

After X-rays on Friday night came back negative, Robles was diagnosed with a bruise, and he should be able to avoid a trip to the injured list.

“I think he’s going to be fine,” Martinez said. “He’s got pretty good strength, it’s just when it gets full extension it bothered him a little bit.”

Fedde heading to rotation

The Nationals are moving right-hander Erick Fedde into the starting rotation while Anibal Sanchez is on the injured list with a left hamstring strain.

Fedde had pitched well at Double-A Harrisburg, with a 2.55 ERA and a 27-to-5 strikeout-to-walk ratio in five games (four starts). His hot start prompted the Nats to add him to their bullpen a little more than a week ago to help fill a need on the big league roster, but Fedde does not believe the move back to a starting role will be a huge adjustment.

“I think that’s something I’m really comfortable with,” Fedde said Thursday. “I’m not too far removed from it, so I think I could give this team five innings for sure, but whatever the coaches say, I can get the job done.”