Rey Mysterio may be 37 years old and on the downside of his Hall of Fame-worthy career in WWE, but he still has a lot to offer and remains an important part of the product even if he is no longer involved in high-profile angles.
Mysterio has pretty much done it all in the WWE, as he is a former one-time WWE Champion, two-time World Heavyweight Champion, six-time Intercontinental Champion, four-time Tag team Champion, as well as a Royal Rumble winner among many other accolades. Very few men boast a resume that resembles anything close to that, and the fact that Mysterio did it all as the ultimate underdog makes it even more impressive.
I can't envision Mysterio ever becoming a world champion again with so many guys above him on the totem pole, but that doesn't mean he needs to be led out to pasture. Mysterio is still excellent in terms of pure wrestling ability, and he continues to appeal to the fans. Also, from a money-making standpoint, there can't be many guys in the company currently who rake in more cash than Mysterio thanks to merchandise sales.
Mysterio's biggest value comes from his experience, however, and the fact that he can help mentor many of the younger guys on the roster. Mysterio has already started to do that with Sin Cara. I obviously don't know how much of a connection they have off camera, but it's likely a pretty strong one. Mysterio is considered one of the greatest luchadores of all-time, and Sin Cara probably hopes to reach a similar level one day, so they have a lot in common.
Putting Mysterio and Sin Cara together in a tag team was a brilliant move by the writers, and it has paid immediate dividends. Not only has Sin Cara improved and been given purpose, but this is precisely the type of thing that can extend Mysterio's career. He is still relevant, as the tag team division is rapidly improving, but he doesn't have to carry the entire load in terms of in-ring work.
Mysterio has had a lot of issues with his knees over the past couple years, and that is a tough injury to have in wrestling. It has definitely caused him to lose a bit of his explosion, but Mysterio is still one of the best pure wrestlers on the entire roster. I'm not sure if he could handle wrestling 15-minute matches on a nightly basis now like he used to, but the presence of Sin Cara ensures that he doesn't have to.
Additionally, Mysterio has breathed new life into the tag-team scene. Just a few months ago, Kofi Kingston and Truth, Primo and Epico and The Prime Time Players were essentially the only teams in the entire company. Since then, Team Hell No has come to the forefront as the Tag Team Champions, but Mysterio and Sin Cara are a great team as well and figure to win the straps sooner rather than later.
The tag team division was really lacking in star power previously, but that is no longer the case. Kane and Daniel Bryan receive most of the credit for that, but Mysterio's contributions shouldn't be forgotten either. He has shined as both a singles and a tag-team competitor in the past, and he has plenty of name recognition. The involvement of Mysterio and other top guys in the tag team scene is what made the fans care again.
If that weren't enough, Mysterio is still one of the best when it comes to putting over his opponents. Mysterio has always been great in that regard because of his diminutive size. It is very easy for him to make other guys look good because they can throw him around like a rag doll. Mysterio and Sin Cara have been winning for the most part, but Mysterio has been good for Titus O'Neil and Darren Young, as they have faced off quite often.
Mysterio seems to realize that he is in a different stage of his career, but he also appears to be the type of unselfish superstar who doesn't mind using his talents to help others. There have been plenty of guys over the years who have been beneficial to Mysterio's development, and the fact that he is able and willing to reciprocate to the younger wrestlers today is great.
There is no telling how much longer Mysterio's body is going to hold up, especially when you take into consideration how much punishment he has absorbed over the years. As long as Mysterio is physically capable of stepping into the ring and performing, though, he will continue to be an asset to the WWE as a whole, as well as everyone who works with.