Strasburg, who was placed on the 15-day injured list Tuesday, is dealing with a stress reaction of the ribs, Mark Zuckerman of MASNSports.com reports.
Strasburg experience renewed discomfort following his between-starts bullpen session last week and now we have an official diagnosis. Thoracic outlet syndrome is notoriously tough to make a full recovery from, and Strasburg could end up being a cautionary tale. He is without a timetable to return.