The move marked the first revelation of a potential injury to Wang’s hip. Manager Davey Johnson said Wang’s personal trainer felt that the pitcher had an issue with his hip that was preventing him from getting his arm in the proper slot for his delivery.

Nationals coaches have been working with Wang on his delivery and Johnson has been concerned with his lack of progress. The 32-year old right-hander was rushing his delivery, which was causing his arm to drag behind his body and prevented him from getting his hand on top of the ball. As a result, his fastball lacked the sink that made him an effective pitcher.

Wang, long a starter, was recently sent to the bullpen, due both to the emergence of Ross Detwiler and his own ineffectiveness as he works through his mechanics. His struggles continued his past two appearances in relief, as he allowed six runs on eight hits in three innings. Overall, he has a 7.61 ERA and a 2-3 record, having started four games this season.

The Nationals signed Wang to a one-year, $4 million for this season, hoping he would regain the form that made him a two-time 19-game winner. Wang missed the season’s first 42 games recovering from a left hamstring injury. Before being put on the DL, he was in danger of being designated for assignment.

The Wang transaction creates a roster spot for Rodriguez, who made seven minor league appearances and waited for his chance to rejoin the Nationals.

Rodriguez was the Nationals closer at the start of the season before he struggled in the role and eventually an injury to his right index finger landed him on the disabled list. Rodriguez said he has been working on his control, the issue that led him to blow three saves and balloon his ERA to 5.14

Rodriguez was on the disabled list since June 7 and made seven appearances across Class AAA Syracuse and Class AA Harrisburg, allowing no hits and runs, striking out seven but walking five. He was at Nationals Park on Tuesday with his family, who were visiting from Venezuela.