The knock could keep him out of the Premier League clashes with Leeds and Wolves, the Europa League game against Braga in between, as well as Belgium's internationals with Switzerland, England and Denmark.
Manager Brendan Rodgers confirmed: "Timothy might be out until after the international break. It's a slight twinge in his hamstring."
Castagne has impressed so far in his first season in the Premier League and has been ever-present in Rodgers' defence, while Evans joined him after missing the first few games of the campaign.
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