BJPenn.com first reported the news, although UFC officials have yet to confirm Siver’s injury.
With 24 days remaining until showtime, it is likely the UFC will keep Penn in the lineup against a new opponent.
Penn is coming out of retirement for the third time. He initially called it quits after getting blasted by Nick Diaz at UFC 137 in October 2011. He decided to return to the cage 14 months later, but was once again was steamrolled, this time at the hands of contender Rory MacDonald.
Instead of walking away again, Penn decided to try and reinvent himself by dropping to featherweight.