Lester is struggling, fine. But Beckett has definitely turned the corner (2.21 ERA over last 5 starts), Buchholz is pretty clearly back to normal, Doubront had a stinker, but he's been very good this year, and DiceK can give us 6 innings, 3-4 ER and keep us in the game.
If the biggest thing we're worried about is Lester, then I promise you that we'll be fine.