#1 Rusev
Rusev was the hottest commodity on SmackDown Live as recently as last year, when 'Rusev Day' was a thing and the audience somehow desperately wanted to see him climb up to the main event position and excel. Unfortunately, he was split up from Aiden English for a feud that went nowhere at all, and the gimmick was dropped.
Since then, he has been sidelined and rumors have even emerged about him asking for some time off. Dave Meltzer has even spoken about Rusev being unhappy and potentially leaving the company in due time once his contract has expired.
So, could this be his farewell feud where a Superstar of his stature is used to get someone like Black over? Rusev is a solid worker and he would be the perfect candidate for Aleister Black's first feud.
It would get Rusev some screen time and could potentially even change his mind about leaving the company.