Jason Lewry is struggling to be fit for the resumption of Sussex's Championship defence on Friday.
Lewry injured a knee at practice before Sunday's totesport League win over Derbyshire and will get the results of a scan today.
He said: "I was just bowling through and felt something go. I've been quite fortunate injury-wise recently and don't usually have any problems with my knees.
"The way it feels at the moment I've got no chance for Friday but hopefully it will improve."
Meanwhile, Tim Ambrose returns in the second team in a three-day match against Kent at Maidstone today after three weeks out with a groin problem.
Ambrose will be hoping to impress ahead of Sussex's four-day game against Kent at Hove on Friday, but his place could be under threat.
The likes of Michael Yardy, Tony Cottey, Luke Wright and Kevin Innes are all starting to find some form at a crucial stage of the season.
Director of cricket Peter Moores said: "We're getting more and more people playing well which is a good sign. I think the two wins we had over Derbyshire and Essex reflect that."
The county go in search of a third successive one-day success against Nottinghamshire in the totesport League at Hove tomorrow (4.10pm) where Mohammad Akram comes in to replace Lewry.
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