The City keeper had suffered with this problem during training in the week but wanted to play. He last just over nine minutes of the game against West Brom this afternoon before he was replaced by Dimi Konstantopolous.
Speaking to the club website, Chris Coleman said: "Keiren said before the game he wanted to start but he's obviously felt a niggle in his lower back where he's been having a bit of pain so as a precautionary measure we thought it better to take him off rather than aggravate the problem."
Pictures from City's 0-0 draw with West Brom can be seen by clicking on the Photo Gallery link on the home page of this site.