As mentioned in the spoilers for this week's episode of SmackDown, it appeared Rusev suffered some sort of injury to his ankle during his match with Ryback. Reports from the arena indicated he was favoring the ankle during the match and they rushed to a disqualification finish before the Bulgarian Brute was helped to the back during a break.
The Wrestling Observer reports Rusev was in a wheelchair and a cast later in the night, so it wasn't just Rusev selling his ankle during and after the match. Then, PW Insider noted that fans saw him at an airport in Philadelphia today in the same situation, wearing a brace with crutches and being wheeled around.
Now, according to Bryan Alvarez on Wrestling Observer Live, Rusev's injury may be bad enough to force him off the upcoming Elimination Chamber event this Sun., May 31, 2015, in Corpus Christi, Texas. He was scheduled to be a part of the Intercontinental title Elimination Chamber match.
WWE has yet to officially comment on the matter.