William Gay filled in for Allen in Week 2, a 20-10 loss to Cincinnati in which the Bengals threw for nearly 300 yards.
The Steelers were able to fight the Bengals off minus a few big plays due to a bigger lineup in which four safeties played in the Steelers' secondary. A similar approach may be used against Chicago, a team with big and physical receivers like Brandon Marshall and Martellus Bennett.
Allen missed most of the preseason with a knee injury. He was expected to be an impact player in his third season, but after a pedestrian opening game, he's missed the last two.
The Steelers will see the return of Heath Miller, as expected. Out since Week 17 of the 2012 season, the Steelers tight end will make his season debut at home Sunday night.
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