You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Professional_wrestling

Context:
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.

Question:
Why couldn't Shawn Michaels defend himself? 

due to excessive blood loss and impaired vision