During HHH's handicap match against the Hurricane and Rosey this past Monday on RAW, the Game was said to have sustained a neck injury, which at one point got so bad, he collapsed in the backstage area.
It's believed that the injury arose from Rosey's 400lb frame leg dropping HHH and landing on his head and neck. As well as the neck injury, it's thought that Triple H may have also suffered a concussion.
After the handicap match, HHH spent the majority of his time backstage icing his neck and keeping a towel round it. As everyone saw, he went back out the for closing segment and re-aggravated his neck injury after taking a bump from Batista. It is when he went backstage after this that he was thought to have collapsed.
The scheduled dark main-event for the show was Shawn Michaels-Batista vs. HHH-Flair, and it's likely that H's injury was the reason that this did not go ahead.
It's also thought that HHH's neck injury was the cause of Stephanie McMahon's no-show to assess OVW talent in Louisville, Kentucky.