Nottingham Forest striker Nathan Tyson could be out for up to six weeks after injuring his hamstring in the 1-0 victory over Swindon.
Promotion-chasing Forest are now third in League One
Tyson, 25, grabbed a fine solo winner but limped off late on and may not return until late March.
The striker missed four games over Christmas with the same type of injury.
He told BBC Radio Nottingham: "It's basically on the same scale as last time. It's so annoying and frustrating - it just seems to keep on happening."
Manager Colin Calderwood said: "It's disappointing because we need all hands to the pump.
"Nathan tends to go on goalscoring runs and we had hoped the goal against Swindon would be the first of many."