It was speculated on Wrestling Observer Radio that The Revival could have possibly be the people who beat up Enzo on Raw.
There were other speculations like Bryan Alvarez suggested that it could be Cass himself, but Meltzer said that he doesn’t think that it is Cass nor does he think it is Apollo Crews and Titus O’Neil.
Meltzer went on to say that The Revival could immediately go after the Hardys after The Hardys face Sheamus and Cesaro in a cage match at Extreme Rules. Meltzer believes though that it would make more sense if the WWE were to use Enzo & Cass to build up The Revival before they face the Hardys.

Source: Wrestling Observer Radio