Source: The Wrestling Observer
Last night, WWE ran an angle on RAW where CM Punk brutally beat Christian, which led to him being replaced on Team Johnny by Drew McIntyre. The WWE.com story started that Christian re-aggravated a prior neck injury, and was not cleared to compete at WrestleMania.
Word is that Christian was pulled from WrestleMania because his ankle is not 100%. WWE made the match with the thought that he would be fully healed in time, but that was not the case.