Jason Lewry gave Sussex an injury worry on the first day of their Championship match with Leicestershire yesterday.
The left-armer has been ruled out for at least ten days after suffering a side strain on the opening day at Grace Road.
Lewry, who returned his best match figures for two years against Essex at Arundel last week, was only able to bowl six overs.
Director of cricket Peter Moores said: "We'll know more tomorrow once it settles down, but it doesn't look too good at the moment.
"He came out of his action a fraction in his fifth over. Fortunately it is quite low down on his side. When it's a strain higher up in the rib area you can be looking at being out for 6-8 weeks."
In Lewry's absence Sussex did well to dismiss the first division's bottom county for 320 with Mushtaq Ahmed taking his season's tally to 60 wickets with 5-93.
The Foxes were struggling at 154-6 and 251-8 but skipper Phil DeFreitas came to their rescue with 103, the tenth century of his career.
Sussex reached 51-0 in reply by the close and Moores believes posting a big first innings total is the key to their hopes of a sixth Championship victory.
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