Task: Question Generation
Input (English): A referee may stop the match when they or official ring physician decides that a wrestler cannot safely continue the match. This may be decided if the wrestler cannot continue the match due to an injury. At the Great American Bash in 2008, Chris Jericho was declared the winner of a match against Shawn Michaels when Michaels could not defend himself due to excessive blood loss and impaired vision. At NXT TakeOver: Rival in 2015, the referee stopped the match when Sami Zayn could not defend himself due to an injury sustained against Kevin Owens for the NXT Championship.
Output (English): In what case can a referee choose to end the match?