The Nationals placed Jason Marquis on the 15-day disabled list with elbow soreness, a sign Marquis's disastrous start to his Nationals tenure may have owed more to injury than Marquis or the team had previously thought. Marquis woke up with stiffness in right elbow Wednesday morning. He alerted team officials and underwent an MRI exam and an arthrogram that afternoon. The test revealed "floating bodies" in his right elbow, General Manager Mike Rizzo said. Marquis will receive a second opinion Thursday from Cincinnati-based physician Tim Kremcheck. As Marquis went 0-3 and accumulated a 20.52 ERA, the Nationals maintained his problem owed to discombobulated mechanics rather than a physical issue. But about 10 days ago, Manager Jim Riggleman said, Marquis "felt a little something, but nothing prohibitive to him pitching."