Brown penned a one-year deal with Preston after leaving Chelsea this summer.
A statement on Preston's club website read: "Preston North End can confirm that Izzy Brown has unfortunately suffered a ruptured Achilles in training, which will keep him sidelined for a significant period of time.
"Izzy suffered the non-contact injury on Monday and has since undergone scans to confirm its severity.
"The midfielder will now begin his recovery at Euxton after suffering the same injury as Patrick Bauer last season.
"Everyone at the club wishes Izzy the very best in his recovery and will support him in any way possible during his rehabilitation."
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