Robert Casey Janssen (born September 17, 1981) is an American former professional baseball pitcher. He pitched for two seasons in various levels of the Toronto Blue Jays' minor league organization before his debut in 2006 as a starting pitcher. Janssen was moved to the bullpen as a middle reliever and spot starter from 2007 to 2011, and in 2012 he was put in the closing role. Janssen also played for the Washington Nationals.