The left back has a stomach strain and will miss the game which is live on Sky Sports. Scott Dann is expected to play some part in Stuart Pearce's team.
Fox,who will be treated by City's medical staff this week told the club website: "I expect to be out of action for about three to four weeks. "i'm gutted that I'm missing out on the opportunity to play for my country. I was really looking forward to the game. Being in Wrexham, it's quite close to home for me and I know some of the boys in the Wales squad so I was looking forward to playing against them.
"I will be going along to watch the game but I just need to concentrate on recovery now. My priority now is to be back ready for pre-season. "Scotty is playing and I'll be there to cheer him on. Hopefully he'll have a good game but like I said, I'm disappointed not to be taking part."