2: Rusev

The WWE's roster is spread incredibly thin at the moment, and the fact that the company has eight of its top stars booked into the World Cup tournament certainly doesn't help proceedings.
Outside of maybe Finn Balor and Dean Ambrose, Rusev is the most popular star not currently booked on the show, so having him replace Daniel Bryan to take on AJ Styles would make a lot of sense.
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Rusev's recent face-turn has helped him re-establish some of his momentum, and while there is no chance he is going to win at Crown Jewel, most fans would appreciate seeing him get another title shot.
Rusev and Styles recently had a match at Extreme Rules back in July, and while it didn't exactly set the world on fire, it was still a highly entertaining encounter.