#1 Rey Mysterio

Rey Mysterio is set to take on Shinsuke Nakamura on SmackDown 1000 to determine who will be the fifth participant in the World Cup at Crown Jewel.
Shinsuke is already the United States Champion, and does not need another title to his name at present, as he was also the last Royal Rumble winner.
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Shinsuke has also not featured on any pay-per-view to defend his United States Championship since SummerSlam in August, and it is unlikely that WWE will again not make him defend his championship at such a major PPV.
Mysterio is returning to the company after a long time, and it is unlikely he will suffer the same fate as Big Show when he goes up to fight for a place in the World Cup. Hence, it is most likely that Mysterio will defeat Nakamura to cement a place in the World Cup, while a new foe will emerge to take on Nakamura for the US title at Crown Jewel.