Forster sidelined with stomach strain
The Royals' leading scorer has been troubled by the stomach problem for an extended period of time and despite a three-week lay-off last month, Forster has not recovered from the injury.
The former Gillingham, Brentford and Birmingham City hit-man had scans this week to assess the damage and he has been told to rest the injury in order to let it heal properly.
"It looks like Fozzy will be out for at least four weeks," Reading boss Steve Coppell told the club's official website.
"The good news is that it's not a hernia and he doesn't need surgery, but it's a muscle strain and will only disappear with the natural healing process over a period of time, so we can just hope that process is a quick one.
"It's difficult to say exactly how long he'll be out, but like any other muscle injury, a hamstring for example, it just needs time and he'll probably be out for four weeks or more."