The shelf life of a big league closer can be short, the careers of Mariano Rivera and Billy Wagner notwithstanding. Maybe the once-dominant Jonathan Papelbon really is showing signs of decline. He blew a save Thursday night as Boston melted down in the ninth inning and lost at Toronto. (Former Mississippi Gulf Coast CC standout Fred Lewis, having a heckuva year with the Blue Jays, got the game-winning sac fly.) Former Mississippi State star Papelbon has six blown saves this year, already matching his career-high from 2006. His ERA has ballooned to 3.26. He posted a 1.85 in 2009. He has nine decisions (4-5), way too many for a closer. Boston has withstood all kinds of injuries to stay in the American League playoff race, but they won’t get into the postseason if Papelbon’s struggles continue. Worst of all, he seems to have lost his fearsome aura; it might be hard to get that back.