Scans on the injury have showed there to be no serious damage and Purse now faces a race against time to be fit for the Premiership clash with the West London side on Saturday.
"I rested Aliou Cisse and Robbie Savage for last night's game but the other changes were enforced with injuries to Purse and Kenna," the Blues boss told www.bcfc.com.
"Purse had a scan and we don't think there is anything seriously wrong so he is 50/50 for the weekend.
"Kenna has been carrying an achilles injury for the past three or four weeks, so it was vital that we tried to protect him."
PRESTON MATCH REPORT
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