As reported on previously, Balor was pulled from the match with what WWE termed an injury, but later reports claimed was a stomach bug of some sort. Ali replaced Balor in the match against Nakamura.
Fightful has followed up on the story, saying that Balor actually was at Smackville, and that many backstage only learned upon his arrival that he had just been hospitalized with the stomach flu.
Fightful adds that Balor left prior to the filming of an angle in which Nakamura was going to take him out, in order to write him out of the match. Balor was apparently unaware of this plan prior to his leaving, and that there "wasn't any malice on his part."
Balor also missed Sunday's live event in Cape Girardeau, MO, where Nakamura once again defeated Ali in an Intercontinental title defense.