We've noted how Rey Mysterio feared he had torn the ACL in his "good" knee a few weeks back but was told by Dr. James Andrews that he wouldn't need surgery and can wrestle with the help of a special brace. While he will be able to wrestle, we likely won't see him in the ring for a while.
For what it's worth, Rey and WWE officials have been on very good terms as of late and they have been begging him to come back. It's said that officials, at least this week, do not want him to leave and consider him a company man for life, even after he retires.
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Guess that makes it a 0% chance of seeing him at WM.