OSEI Sankofa has suffered an Achilles injury.
The Blues right-back picked up the problem during training.
And he is expected to be sidelined until at least next week.
"You have to be sensible when it concerns your Achilles," said Shrimpers manager Steve Tilson.
"You can't take any risks and that's why Osei didn't play at Canvey Island last night.
"He won't be involved at Chelmsford City on Saturday either but we are confident he will be back training next week."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here