(AP)- He has thrown more passes in the preseason than starter Ben Roethlisberger. That doesn't mean the Steelers have seen nearly enough of their new backup quarterback, Byron Leftwich.

Leftwich was signed by the Steelers after Charlie Batch broke his collarbone on Aug. 8. He's expected to get most of the playing time Thursday when the Steelers face the Carolina Panthers in their fourth and final exhibition game. And it's not only because they want to give Leftwich as many preseason snaps as possible in an offense he began learning only this month.

The Steelers still don't know how quickly Batch can return. He isn't expected back until the third game of the season at the earliest.

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