The Washington Nationals have lost Gio Gonzalez for the next few weeks. The Cy Young contender has what the Nationals are calling soreness and inflammation in his pitching shoulder and will give him time to let that calm down, according to Adam Kilgore of the Washington Post.
Gonzalez was diagnosed after having an "enhanced MRI." This is another term for a contrast MRI, which is a normal tool for orthopaedists. A dye is injected into the joint, allowing for a clearer view of the structures, as the video here shows. The Nats said there was no structural damage seen on the enhanced MRI.
So we know what it's not, but pain and inflammation don't just happen. Gonzalez has something wrong inside his pitching shoulder, and absent a structural cause, the usual diagnosis is either impingement or bursitis. Bursitis could be easily seen on a contrast MRI, so it's safe to assume that the Nats aren't playing word games with us.
Add in another piece of evidence, in that Gonzalez told the Washington Post that he was having trouble finding a consistent arm slot, the lean would be to impingement. That indicates a generalized inflammation that is causing some of the structures inside the shoulder to be restricted from their normal movement or even squeezed inside the shoulder.
With Gonzalez on the disabled list, the Nats will go to work trying to remove the inflammation. Rest and treatment should get him more comfortable and at the point where he can get back on the mound; the hope is that his arm will comfortably go back to its natural position. Oddly, comparing his last two starts, it appears that Gonzalez was actually raising his release point, which is opposite of what a pitcher normally does when his shoulder is sore.
The Nats historically have issues keeping their pitchers healthy. While the team was actually in the top 10 for the first time since moving to Washington in terms of injury stats last year, their back in their normal spot early this year. The team has lost about $19.3 million worth of value so far this season. In terms of pure days lost, they're near the bottom again. (Data from my proprietary Injury Database.)
Losing Gonzalez for a short period of time shouldn't devastate the Nationals, but their overall problems with health are one reason that they consistently underperform their expectations and talent.