There had to be a breaking point for Cubs manager Dale Sveum. It finally came Monday, and All-Star shortstop Starlin Castro is on "last straw'' alert in the wake of a 3-2 loss Monday and four-game sweep at the hands of the San Francisco Giants. With one out in the fifth inning, the Cubs leading by a run and the bases full of Giants, Brandon Crawford hit into a fielder's choice at second base. Castro took the relay from Darwin Barney but didn't attempt the throw to first for the double play.