Charlton defender Jonathan Fortune faces at least six months on the sidelines after rupturing his Achilles.
The centre-half, who is out of contract in the summer, underwent an operation on Monday morning after suffering the injury during Saturday's goalless draw against Hartlepool.
"It's a real shame," said manager Chris Powell.
"He's got back in the team and his contract expires soon so he's been trying to express himself.
"It's put me on a downer because you don't want to see players hurt."