Starlin Castro may find himself on the bench soon if his lack of focus continues, or at least that's the latest threat from his manager.

Castro's second mental gaffe in the four-game sweep by the Giants occurred during the fifth inning of the Cubs' 3-2 loss Monday when the 22-year-old shortstop forgot how many outs there were after taking a throw at second from Darwin Barney.

"It's the last straw," Cubs manager Dale Sveum said. "He better start getting his head in the game, period."

Castro began running off the field after the second out, neglecting to throw to first to try to double up Brandon Crawford, as the tying run scored from third.

There was little chance Castro could've thrown out Crawford, but the gaffe was too extreme for Sveum to overlook.