Derbyshire head coach Karl Krikken fears that South African all-rounder Greg Smith will be out for two weeks or more with a shin injury.
Smith has not played in the last two games and his absence has coincided with back-to-back FL t20 defeats.
But Krikken told BBC Radio Derby they cannot rush Smith back: "There is a hot spot on his shin and if he plays it will get worse and could crack.
"We are hoping another week or two but we don't know."
Smith is almost certain to miss the Twenty20 games against Yorkshire (22 June), Worcestershire (24 June) and Warwickshire (25 June).
He is also likely to miss the Championship match against Glamorgan which starts on Monday and is a doubt for the T20 fixtures against Nottinghamshire (1 July) and Lancashire (3 July).
Krikken added: "We have to manage it and keep him off his feet. We need to take down the load and get him back fit and well."