And in retrospect, those blown leads couldn't have been much of a surprise to their team's fan bases, even after seasons of success.
Taking them in order:
Joe Nathan, Minnesota, Game 2 against New York. Nathan's September/October ERA was 3.38. Of more alarm, he had given up four homers in that period — more than in the rest of the season combined — and pitched 16 innings, almost 50 percent more than the other closers involved in these blown saves. He was, of necessity, worked hard down the stretch, and he's about to turn 35.
Jonathan Papelbon, Boston, Game 3 against Anaheim. No real issues here; he had last blown a save opportunity in July, his September/October ERA was 1.58, he hadn't walked a batter since August 24. Still, there were rumblings in the Nation that he wasn't quite as dominant in 2009 as they're used to seeing.
Huston Street (photo above), Colorado, Game 4 against Philadelphia. For that matter, he took the loss in Game 3, which wasn't a save opp. Street's September/October ERA (3.38) wasn't much worse than his season ERA (3.09), but he had a three-week gap in September in which he didn't pitch, and his August ERA was 5.79.
As the boilerplate financial services disclaimer says, past results do not guarantee future performance.