Felipe Rivero has been placed on the DL. Jonathan Newton / The Washington Post)

The Nationals placed left-handed reliever Felipe Rivero, who made his major league debut Friday, on the disabled list Wednesday with gastrointestinal bleeding and called up left-handed reliever Matt Grace from Class AAA Syracuse. The move was surprising because there were no obvious indications that Rivero was hurt. The team also announced that Grace is available out of the bullpen for Wednesday’s game.

The Nationals have shuffled their bullpen around a lot already this season. Grace will become the third reliever to be called up for the first time in the past week, joining Rivero and right-hander Rafael Martin. Injuries to Casey Janssen and Craig Stammen, and Xavier Cedeño’s poor performance, have forced the Nationals to alter their bullpen more than expected.

Rivero appeared in his first and only major league game Friday, allowing one run in one inning of work. He hasn’t pitched since and his disabled list stint is retroactive to Saturday. But in two of the three games the Nationals have used a left-handed reliever since, the situations were more suited for veteran Matt Thornton.

Like Rivero, Grace, 26, is in the major leagues for the first time in his career. The left-hander reliever has allowed three runs in 7 2/3 innings at Syracuse so far this season and held left-handed batters to a .167 average. He hasn’t pitched since Sunday.

Grace enjoyed a breakout 2014 season that landed him a spot on the Nationals’ 40-man roster in the offseason. The Nationals drafted Grace in the eighth round of the 2010 draft out of UCLA, where he was a reliever on a star-studded pitching staff that included Trevor Bauer and Gerrit Cole. He tried starting in the minor leagues but converted back to relieving.

Last season, he posted a combined 1.17 ERA over 77 innings across Class AA Harrisburg and Syracuse. Relying heavily on a low-90s fastball with a lot of sink, he induces plenty of groundballs. Although his walk rate is a tad above average, he allowed only one home run all last season. He also held left-handed batters to a .144 average.

In another minor bullpen move Wednesday, the Nationals traded Cedeño to the Dodgers for cash considerations, eight days after designating him for assignment. Cedeño made the Nationals as the second left-handed reliever out of spring training but lasted only a week with the team.

Cedeño, 28, appeared in five games this season and allowed two runs. Even though he was a left-handed specialist, nine of the 15 batters he faced were right-handed batters. In three seasons of up and down between Syracuse and the Nationals, Cedeño posted a 3.38 ERA in 16 innings.

The Nationals counted on Cedeño to help round out their bullpen but it backfired. Late in spring training, the Nationals traded away veteran left-hander Jerry Blevins, billing the move as dealing from a position of depth to fill an outfield need because of injuries.