During last night's episode of RAW, it quickly became apparent that Rusev has been pulled from Super ShowDown after commentator Tom Phillips said that Rey Mysterio is in the match despite there being a graphic showing the Bulgarian Brute. Later, imagery was shared which featured the Master of the 619, so something has obviously changed.
What that might be is hard to say, but it's no secret that Rusev has been clashing with WWE over signing a new contract, so it's possible that something could have changed behind the scenes. It could be something as simple as creative plans being shaken up, but don't be surprised if we get an update soon about what's happening with Rusev now.
In related news, WWE has also started hyping Mysterio's return to RAW next week as it's been confirmed that he will team up with Humberto Carrillo to battle Angel Garza and United States Champion Andrade. As for Super ShowDown, Andrade, R-Truth, Bobby Lashley, AJ Styles, and Erick Rowan will all compete in the match alongside Mysterio.