Mattheus broke his hand by slamming it on his locker after allowing five runs against the Padres on Sunday. Mattheus didn't reveal that something was wrong until the next day when he tried to play catch in San Francisco.
Mattheus is considered a late-inning reliever, who usually pitched in the seventh inning. He had a 4.96 ERA before he was put on the disabled list.
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time. He also could be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.