Rey Mysterio has been sidelined from WWE since April, when he suffered a torn groin and a ruptured eardrum. The former World Champion is reportedly nearing full fitness ahead of a return, but he had to pause his rehab to send a message on what would have been Eddie Guerrero's 58th birthday.Eddie's daughter, Sherilyn Guerrero, shared a heartbreaking update on her father's birthday, accompanied by an emotional video. Mysterio felt the need to share his own message on the Instagram post, noting that he still misses his friend two decades after his passing.Rey Mysterio has commented on Sherilyn Guerrero's post [Image credit: Sherilyn Guerrero's Instagram]"Miss him so much!!" he wrote.Mysterio was one of Eddie Guerrero's closest friends and was only part of the high-profile match between the two men at SummerSlam 2005, months before his passing.The two men fought for custody of Mysterio's son, Dominik, who has since grown up within the business and has become a WWE Superstar himself.Rey Mysterio could be the next WWE star to announce retirementRey Mysterio and his son Dominik continue to be at odds in WWE, but when The King of Mystery makes his return to the company in a few months, it could be post John Cena's retirement. View this post on Instagram Instagram PostAJ Styles has also announced his retirement, noting that it will happen when his WWE contract expires in 2026. Mysterio appears to be pushing for one more match against his son, which could be the official passing of the torch between the two men.It's unclear when Mysterio will be able to make his return after stepping out of WrestleMania earlier this year, but he will likely be pushed towards another match against his son, who has become one of WWE's fastest rising stars in recent years.