Preston defender Sean St Ledger suffered a hamstring injury in his side's 1-0 friendly defeat by Oldham at Boundary Park on Saturday.
Teenage Latics forward Ryan Brooke scored the only goal of the game when he slotted underneath North End goalkeeper Andy Lonergan in the 40th minute.
St Ledger pulled up shortly before the interval and will need to be assessed before Darren Ferguson's men kick off the new Championship season at home to Doncaster next weekend.