Portugal striker Ricardo Sa Pinto could be out for as long as six months after tearing a cruciate ligament in his knee.
The Sporting Lisbon star was injured ten minutes from the end of Saturday's 2-1 victory over Belenenses.
Club doctor Gomes Pereira confirmed: "He should be out for between four and six months."
That means that Sa Pinto will miss the rest of the season, which will come as a bitter blow to a club still reeling after the sacking of coach Augusto Inacio last week.
Sporting won their first Portuguese title for 18 years last season but, despite lying just two points behind league leaders Porto, they appear a club in crisis now.
They are without a manger and their debts are reported to be spiralling.
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