When Washington Nationals reliever Sean Burnett took a comebacker off his left thumb against the Milwaukee Brewers on Aug. 23, he was settling into a role as one of the team's late-inning fixtures. Burnett had made six of his previous nine appearances with the game tied or the Nationals ahead by three or less, and eight of those nine appearances had come in the seventh inning or later. He was on track to take over at least part of the setup role Joe Beimel vacated when he was traded Jul...