#1 R-Truth
R-Truth has been a part of the WWE for a long time now, and the veteran has continued to entertain the fans with his mic skills, as well as in-ring talent. R-Truth recently won the Mixed Match Challenge with Carmella, and is set to enter the 2019 Royal Rumble match at #30. However, given how he has been booked on SD Live, some other superstar may take his spot in the Rumble that night.
Also Read - 4 WWE Superstars who could take the #30 spot instead of R-Truth
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R-Truth's character has a funny element, and possesses good sense of humor. So, the WWE can use him as a special guest referee in the throwaway matches which take place on SmackDown Live every week.
This would provide the fans some comic relief during the 2 hours show, along with having the potential of giving R-Truth a good storyline on SmackDown Live.