Colchester United believe striker Steven Gillespie has suffered a fractured arm.
The 25-year-old fell awkwardly in Friday's 1-1 draw at Brentford.
"We believe Steven has fractured his arm and it looks like he might have to have an operation," U's boss John Ward told the club website.
"We are always talking about our players working hard and Steven was doing that as we went to bloke a clearance down the line."
Injury prevented Gillespie from featuring in a league match until January this season, but since then he has scored nine goals in 18 games.