Sammy Solis in spring training. (John McDonnell/The Washington Post)

Sammy Solis, one of the Nationals’ top pitching prospects, has been shut down with left elbow discomfort, according to Mark Scialabba, the Nationals’ director of player development. Solis has not pitched since May 26, his first start for Class AA Harrisburg since coming off the disabled list with a back issue that emerged in spring training.

Solis, 25, has been evaluated by the Nationals team doctor. The injury is a concern not simply because it involves the pitcher’s elbow, but also because Solis already underwent Tommy John surgery in 2012. Solis returned from the surgery last season and posted a 3.32 ERA over 59 2/3 innings, the majority at Class A Potomac.

In his lone start at Harrisburg, Solis allowed nine runs, eight earned, over 3 1/3 innings. Including rehab starts, he gave up nine earned runs over 14 2/3 innings this season.

The Nationals have been bullish on Solis since they drafted him in the second round in 2010 out of the University of San Diego and handed him a $1 million signing bonus, more than the recommended slot for the pick. He was pegged as a quick-to-the-majors pitcher with a power sinker. Baseball America rated Solis the Nationals’ No. 6 prospect this season. But his time as a professional has been mired by injury.

Solis had elbow surgery in 2012. He missed nearly a month last season with a shoulder issue. He was expected to compete for a bullpen spot this spring training, but was limited to two outings because of the back issue.

The rise of elbow injuries this season have been a hotly-discussed issue and the Nationals have endured their share in the minor leagues. Right-handed reliever Erik Davis, left-handed starter Danny Rosenbaum and prospect Matt Purke have all undergone Tommy John surgery.