"Nedum is likely to miss out because of tight hamstrings," City boss Mark Hughes told the club's official website.
"It's unfortunate for him and a shame because he did really well in the second-half against Hull, and again at Blackburn last Sunday.
"It was a good opportunity for him but when you have not played that many games sometimes it can be difficult to build up the match strength that you need.
"He is a little bit compromised at the moment but hopefully it is only a six to eight day injury and he will be ok for the trip to Portsmouth."