San Francisco 49ers backup running back Reggie Bush could be back on the shelf after aggravating a calf injury in Sunday's 30-27 loss at the New York Giants.

Bush was hurt on his first carry on San Francisco's opening drive, getting dropped for a one-yard loss on his only carry. Former Australian rugby player Jarryd Hayne replaced Bush and had two carries for nine yards.

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Signed to a one-year contract in the offseason, the oft-injured Bush was hurt in a season-opening win over Minnesota, carrying twice for eight yards.

Bush missed the following two games before returning to the lineup in Week 4 against the Green Bay Packers. He was stopped for no gain on his lone carry and had one reception for six yards.

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