Essex's injury concerns have been worsened by the news Maurice Chambers and Michael Comber are set for spells on the sidelines.
With Scott Styris and Graham Napier already out, fellow all-rounder Comber is expected to have a two-month lay-off with a damaged foot.
Fast bowler Chambers has torn a quadricep muscle and will be missing for up to three weeks.
Napier is being touted for a return on 15 July.
He has not featured since picking up a hamstring complaint in last Monday's Twenty20 defeat by Surrey.
Essex are hopeful Scott Styris will recover from a calf tear in time for the match against Kent at Canterbury on 1 July.
Chambers and Comber have yet to make appearances in this year's competition, but were being primed to ease the team's injury problems.
Meanwhile, James Foster has received three penalty points under the England and Wales Cricket Board's disciplinary code.
The Essex keeper was reported by umpires David Millns and Trevor Jesty for showing serious dissent during the loss to Surrey.
The penalty will remain on his record for two years.
The Chelmsford club's chances of progressing from the group stage took a further hit when Friday's clash with Gloucestershire was rained off.
They now sit seventh in the South Group with just two wins from seven games.